KR20230091968A - Polyethylene powder and molded body - Google Patents

Abstract

In pulse NMR, the relaxation time T of each component and the abundance ratio R of each component when 3-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method are <Requirement (1)> and <Requirement (2) >, polyethylene powder.
<Requirement (1)>
At 180°C, the entanglement index obtained by (Formula I) is 12 to 25 ms.
(entanglement index) = T _α × R _α / (R _α + R _β ) + T _β × R _β / (R _α + R _β ) ... (Equation I)
T _α : relaxation time of the low-motile component α (ms)
R _α : presence ratio of low-motile component α (%)
T _β : relaxation time of intermediate component β (ms)
R _β : abundance of intermediate component β (%)
<Requirement (2)>
At 180°C, the intermediate component ratio determined by (Formula II) is 0.25 to 0.5.
(intermediate component ratio)=R _β /(R _α +R _β ) … (Equation II)

Description

Polyethylene powder and molded body

The present invention relates to polyethylene powder and molded products.

Ultrahigh molecular weight polyethylene powder is molded by various molding methods such as melt stretching, injection molding, extrusion molding, and compression molding, and is used for a variety of applications such as films, sheets, microporous membranes, fibers, foams, and pipes.

In recent years, demand for polyethylene powder is increasing for the use of microporous membranes and fibers, and in particular, demand as a raw material for separators, which are important members of lithium ion batteries and lead-acid batteries, is rapidly expanding.

Ultrahigh molecular weight polyethylene powder has a high viscosity when melted and poor molding processability, so when producing a microporous film or high-strength fiber, wet extrusion processing is generally used in which extrusion processing is performed while dissolving in a predetermined solvent. During this wet extrusion process, if the dispersibility of the polyethylene powder in the solvent is poor, the high molecular weight material is localized in the molded object, resulting in dimensional unevenness such as width or thickness, or non-melting, which leads to deterioration of the physical properties and appearance of the molded object. Therefore, the improvement of the dispersibility in the solvent of polyethylene powder is calculated|required.

In addition, when a microporous membrane made of polyethylene powder is used as a battery separator, it has a function of isolating the positive electrode and the negative electrode to prevent a short circuit while allowing only ions to pass through, and melting the pore portion when a large current flows, thereby reducing the amount of ions. It is necessary to have a shut-down function to block permeation and prevent runaway cell reaction, that is, a function to block pores at a temperature lower than the temperature of thermal runaway, a so-called fuse effect, and to have high mechanical strength.

In recent years, the demand for high capacity and high output has rapidly increased, centering on in-vehicle batteries, and as a result, a further improvement in mechanical strength and dimensional stability is required for separators for batteries. In addition, since expansion and contraction of electrodes increase when charging and discharging are performed with higher capacities of electrodes, creep resistance capable of withstanding long-term stress is becoming more important for separators for batteries.

Patent Document 1 discloses a technique for obtaining a film and microporous membrane having high permeability, low heat shrinkage, excellent mechanical strength and heat resistance by using a polyolefin resin containing an ultra-high molecular weight ethylene polymer having a specific limiting viscosity and melting point. has been

Further, in Patent Document 2, by using a polyethylene resin composition containing an ethylene homopolymer having a specific melt flow rate, a specific molecular weight distribution, and a specific elution amount measured by cross-fractionation chromatography, molding processability is excellent and air permeability is excellent. A technique for obtaining a microporous film having high mechanical strength and excellent mechanical strength is disclosed.

Japanese Unexamined Patent Publication No. 2018-090744 Japanese Patent No. 5840743

However, in the technology disclosed in Patent Literature 1, although the obtained microporous membrane has excellent mechanical strength and dimensional stability, no study has been made to improve molding processability and creep resistance, and there is a possibility of uneven mechanical strength. In addition, there is a problem that there is a possibility that the electrode may not be able to withstand the long-term stress caused by the expansion and contraction of the electrode accompanying charging and discharging.

Further, in the technology disclosed in Patent Literature 2, although both molding processability and mechanical strength are achieved, there is a problem that no study has been made to improve dimensional stability or creep resistance.

Accordingly, an object of the present invention is to provide a polyethylene powder capable of achieving both excellent molding processability and high mechanical strength, and capable of obtaining a microporous membrane having excellent dimensional stability and creep resistance.

As a result of intensive research to solve the above problems, the inventors of the present invention, in pulse NMR, when a free induction decay curve obtained by the Carr Purcell Meiboom Gill method is approximated by three components, the relaxation time T and the component ratio R of each component It was found that the polyethylene powder satisfying this predetermined relationship could solve the problems of the prior art described above, and the present invention was completed.

That is, this invention is as follows.

〔One〕

In pulse NMR, the relaxation time T of each component and the abundance ratio R of each component when 3-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method are (2) that satisfies >;

polyethylene powder.

<Requirement (1)>

At 180 ° C, the entanglement index obtained by the following (Formula I) is

12 ms or more and 25 ms or less.

(entanglement index) = T _α × R _α / (R _α + R _β ) + T _β × R _β / (R _α + R _β ) ... (Equation I)

T _α : relaxation time of the low-motile component α (ms)

R _α : presence ratio of low-motile component α (%)

T _β : relaxation time of intermediate component β (ms)

R _β : abundance of intermediate component β (%)

<Requirement (2)>

At 180 ° C, the intermediate component ratio determined by the following (Formula II) is

It is 0.25 or more and 0.5 or less.

(intermediate component ratio)=R _β /(R _α +R _β ) … (Equation II)

〔2〕

In pulse NMR, for the component abundance R obtained by 3-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method,

The polyethylene powder according to [1] above, wherein the rate of change in the proportion of the low-moisture component present at 180°C is -5% or more and 10% or less.

[3]

In pulse NMR, for the component abundance R obtained by 3-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method,

The polyethylene powder according to [1] or [2] above, wherein the rate of change in the proportion of the highly mobile component present at 180°C is 50% or less.

〔4〕

The polyethylene powder according to any one of [1] to [3], wherein the isothermal crystallization time at 125°C is 5 minutes or less.

[5]

The polyethylene powder according to any one of [1] to [4], wherein the viscosity average molecular weight is 200,000 or more and 10,000,000 or less.

[6]

The polyethylene powder according to any one of [1] to [5], wherein the median diameter is 50 μm or more and 250 μm or less.

[7]

The polyethylene powder according to any one of [1] to [6], which is for battery separators.

〔8〕

A molded product of the polyethylene powder according to any one of [1] to [7].

[9]

The molded article according to [8] above, which is a microporous film.

[10]

The molded article according to [8] above, which is a fiber.

[11]

The molded body according to [8] above, which is a battery separator.

According to the present invention, it is possible to provide a polyethylene powder capable of achieving both excellent molding processability and high mechanical strength, and capable of obtaining a microporous membrane having excellent dimensional stability and creep resistance.

Hereinafter, the mode for implementing the present invention (hereinafter, also referred to as "this embodiment") will be described in detail.

In addition, the present embodiment below is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be implemented with various modifications within the scope of the gist thereof.

[Polyethylene powder]

In the polyethylene powder of the present embodiment, in pulse NMR, when a free induction decay curve obtained by the Carr Purcell Meiboom Gill method is approximated by three components, the relaxation time T of each component and the abundance ratio R of each component are the following <requirements (1)> and <Requirement (2)> are satisfied.

In addition, the abundance ratio R (%) makes the sum of the three components 100%.

<Requirement (1)>

At 180°C, the entanglement index determined by the following formula (I) is 12 ms or more and 25 ms or less.

(entanglement index) = T _α × R _α / (R _α + R _β ) + T _β × R _β / (R _α + R _β ) ... (Equation I)

T _α : relaxation time of the low-motile component α (ms)

R _α : presence ratio of low-motile component α (%)

T _β : relaxation time of intermediate component β (ms)

R _β : abundance of intermediate component β (%)

<Requirement (2)>

At 180°C, the intermediate component ratio determined by the following formula (II) is 0.25 or more and 0.5 or less.

(intermediate component ratio)=R _β /(R _α +R _β ) … Formula (II)

When the polyethylene powder of the present embodiment has the above configuration, the effect of obtaining a microporous membrane capable of achieving both excellent molding processability and high mechanical strength and excellent dimensional stability and creep resistance is obtained.

Hereinafter, the structure of the polyethylene powder of this embodiment is demonstrated.

The polyethylene powder (hereinafter sometimes simply referred to as "powder") of the present embodiment is constituted by an ethylene-based polymer.

Examples of the ethylene-based polymer include ethylene homopolymers and copolymers of ethylene and other comonomers copolymerizable with ethylene (for example, binary or tertiary copolymers).

The bonding form of the copolymer may be random or block.

Although it does not specifically limit as another comonomer, For example, an alpha-olefin, a vinyl compound, etc. are mentioned. Other comonomers can be used individually by 1 type or in combination of 2 or more types.

Although it does not specifically limit as alpha-olefin, For example, C3-C20 alpha-olefin is mentioned, Specifically, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1 -octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene and the like. Among these, the other comonomer is preferably propylene and/or 1-butene from the viewpoint of further improving the heat resistance and strength of the microporous membrane.

Although it does not specifically limit as a vinyl compound, For example, vinyl cyclohexane, styrene, these derivatives, etc. are mentioned.

Moreover, as another comonomer, you may use non-conjugated polyenes, such as 1, 5- hexadiene and 1, 7- octadiene, as needed.

(entanglement index and intermediate component ratio at 180 ° C)

As a known index for estimating the entanglement of molecular chains in polyethylene powder, evaluation of dynamic viscoelasticity is mentioned.

In evaluation of dynamic viscoelasticity, the average degree of entanglement of the molecular chains of the entire resin can be obtained in order to evaluate the degree of entanglement of the molecular chains from the responsiveness when stress is applied to the resin. However, when controlling a plurality of physical properties such as mechanical properties and molding processability at the same time, it is preferable to treat a plurality of entanglement components present in the resin separately, so the average entanglement degree of molecular chains alone is insufficient as an index.

The inventors of the present invention, in order to determine a raw material suitable for a molded article with well-controlled physical properties such as mechanical properties and molding processability, pulse NMR at 180 ° C. The entanglement index calculated from the measurement of and the intermediate component ratio were used together to accurately evaluate the degree of entanglement of the polyethylene powder.

In the pulse NMR measurement, the Carr Purcell Meiboom Gill method, a measurement method suitable for evaluating the motility of polymers with active molecular chain motions, for example, rubbery polymers, was used.

As a result, in pulse NMR, when the free induction decay curve obtained by the Carr Purcell Meiboom Gill method is approximated by three components, the relaxation time T and component ratio R of each component are the following <requirement (1)> and <requirement ( 2) It was found that a polyethylene powder that simultaneously satisfies > is surprisingly suitable as a raw material for a microporous membrane from the viewpoint of mechanical properties and molding processability.

<Requirement (1)>

At 180°C, the entanglement index determined by the following (Formula I) is 12 ms or more and 25 ms or less.

(entanglement index) = T _α × R _α / (R _α + R _β ) + T _β × R _β / (R _α + R _β ) ... (Equation I)

T _α : relaxation time of the low-motile component α (ms)

R _α : presence ratio of low-motile component α (%)

T _β : relaxation time of intermediate component β (ms)

R _β : abundance of intermediate component β (%)

<Requirement (2)>

At 180°C, the intermediate component ratio determined by the following (Formula II) is 0.25 or more and 0.5 or less.

(intermediate component ratio)=R _β /(R _α +R _β ) … (Equation II)

In the polyethylene powder of the present embodiment, the range of the entanglement index determined by the above (Formula I) at 180 ° C. is 12 ms or more and 25 ms or less, preferably 13 ms or more and 22 ms or less, more preferably 14 ms or more and 20 ms or less.

When the three-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in the pulse NMR of the polyethylene powder of the present embodiment, the low-mobility component α corresponds to the portion in which the molecular chains are strongly intertwined in the polyethylene powder And, it is considered to be a component that is likely to remain in the microporous membrane without coming loose during the molding process. On the other hand, the intermediate component β in the polyethylene powder of the present embodiment corresponds to a portion in which molecular chains are more weakly entangled than the low mobility component α, and is considered to be a component that is easily released in the molding process. In addition, as the degree of entanglement of each component increases, the value of the relaxation time T decreases.

When the entanglement index obtained by the above formula (I) at 180 ° C. is 12 ms or more, the stress remaining after molding is reduced, so a microporous membrane with excellent dimensional stability tends to be obtained.

On the other hand, when the entanglement index obtained by the above formula (I) at 180 ° C. is 25 ms or less, the degree of entanglement of the molecular chains in the polyethylene powder becomes stronger, so the microporous membrane obtained by molding has high mechanical strength and excellent It tends to exhibit creep resistance.

In the polyethylene powder of the present embodiment, in pulse NMR, when a three-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method, the intermediate component ratio at 180 ° C. obtained by the above (Formula II) is 0.25 or more It is 0.5 or less, Preferably it is 0.25 or more and 0.45 or less, More preferably, it is 0.3 or more and 0.4 or less.

When the intermediate component ratio at 180 ° C. obtained by the above (Formula II) is 0.25 or more, the molding processability of the polyethylene powder increases, and a microporous film with excellent appearance tends to be obtained.

On the other hand, when the intermediate component ratio at 180 ° C. is 0.5 or less, since an appropriate amount of molecular chain entanglement points remain in the microporous film obtained by molding processing, stress propagates easily and creep resistance tends to be excellent there is

In general, when the degree of entanglement of the molecular chains of the polymer is strong, the mechanical strength of the obtained microporous membrane is improved, but the molding processability deteriorates because the dispersibility of the molecular chains of the polymer is low. Irregularity occurs. In this way, if there is unevenness in the thickness or the like of the microporous membrane, a portion having weak mechanical strength is generated, which tends to be a starting point of deterioration.

On the other hand, when the degree of entanglement of the molecular chain of the polymer is weak, the molding processability is good, but the mechanical strength is low.

Since the strength of the degree of entanglement of the molecular chain of the polymer is well controlled in the polyethylene powder of the present embodiment, both mechanical strength and moldability can be improved when a microporous membrane is produced.

In addition, when there are many entanglement points of the molecular chain of the polymer in the microporous membrane, the mechanical strength is high and the propagation of stress is easy, so the creep resistance is excellent, but the residual stress is large, so the dimensional stability tends to deteriorate there is Deterioration in dimensional stability leads to short circuit or deterioration when the microporous membrane is used as a battery separator.

On the other hand, when there are few entanglement points of the molecular chain of the polymer, although it has excellent dimensional stability, there is a tendency that sufficient mechanical strength is not developed, and since stress is difficult to propagate, local loads are easily applied, thereby forming a microporous membrane. When used for a separator for a battery, there is a tendency that the volume change of the electrode accompanying charging and discharging cannot be tolerated.

Since the amount of entanglement points in the molecular chain of the polymer is well controlled, the polyethylene powder of the present embodiment is excellent in dimensional stability, and can have sufficient mechanical strength and creep resistance.

In order for the entanglement index at 180 ° C. obtained by the formula (I) and the intermediate component ratio obtained by the formula (II) to show values within the predetermined range described above, in the polyethylene powder, they are strongly entangled with each other It is necessary that the degree of entanglement of the molecular chains present has a certain strength and the proportion of weakly entangled molecular chains is high.

And as a characteristic of the polyethylene powder which satisfies these, the containing of several polymer components with different entanglement states etc. are mentioned.

As a method for controlling the entanglement index at 180 ° C. obtained by the above formula (I) and the intermediate component ratio obtained by the above formula (II), the state of the catalyst is changed during polyethylene polymerization, or the polymerization behavior is greatly different. A method of mixing a plurality of catalyst components, and the like are exemplified.

Specifically, using a polymerization catalyst having large pores and containing a brittle carrier, polymerizing under high-pressure conditions in the first half of the polymerization, and then setting the slurry concentration in the polymerization reactor to 40% by mass or more, or reducing large pores After pre-polymerization of a polymerization catalyst containing a support that has and is easily cracked, the stirring speed in the polymerization reactor is set to 300 rpm or more, and a plurality of catalysts having greatly different distributions of active species on the surface of the support are mixed and used. things, etc.

In the synthesis of the polymerization catalyst used in the polymerization reaction of polyethylene, by using a carrier having large pores, the amount of active species supported in the pores is increased, and in the polymerization reaction of polyethylene, polymerization of polyethylene in the pores can promote In addition, since molecular chains of growing polyethylene tend to cross each other in the space within a narrow pore, it becomes possible to polymerize a component having a strong molecular chain entanglement.

On the other hand, by making the support used for the polymerization catalyst easy to crack, the catalyst is easily cracked during polyethylene polymerization due to the increase in pressure in the pores accompanying the growth of the molecular chain of polyethylene.

In addition, when the catalyst is cracked by increasing the stirring strength, it becomes difficult for molecular chains of growing polyethylene to cross-link, and it becomes possible to polymerize components with weak molecular chain entanglement.

In addition, by adding a thickener after synthesis of the carrier or adjusting the pressure difference between the transfer source and the transfer destination during catalyst transfer to be small, the catalyst carrier can be prevented from cracking before the polymerization process, and multiple entanglement degrees of molecular chains are different. of polyethylene components can be produced during polymerization.

The pulse NMR measurement applied to the measurement of the polyethylene powder of this embodiment is specifically performed by the following method.

First, a sample tube filled with polyethylene powder to a height of 1 cm from the bottom was put into a Bruker TD-NMR apparatus (model: minispec mq20) set so that the internal temperature of the sample tube was 30 ° C. The temperature of the sample tube is raised according to the conditions>.

The temperature shown in the following <temperature rising conditions> is a value obtained by measuring the internal temperature of the sample with a thermocouple.

<Temperature Raising Conditions>

(1) Set to 30 degreeC and leave still for 5 minutes.

(2) The temperature is raised to 180°C at a rate of 5°C/min.

(3) After heating up to 180°C, it is left still for 25 minutes.

After completion of the temperature rise in the above-described procedure, the polyethylene spin-spin relaxation time (T ₂ , sometimes simply referred to as “relaxation time T” in the present specification) is measured according to <measurement conditions> shown below.

After completion of the measurement, the same measurement is repeated 3 times, and a total of 4 measurements are performed.

<Measurement conditions>

Magnetic Field Strength: 0.47T

Measurement nuclide: ¹ H (20 MHz)

Measurement method: Carr Purcell Meiboom Gill method

Total number of times: 256 times

Repeat time: 3 seconds

Interval between first 90° and 180° pulses (τ): 0.04 milliseconds

Total number of echo signals: 6400

For the free induction damping (FID) obtained by the fourth measurement out of all four measurements described above, curve fitting is performed using the analysis program TD-NMR-A manufactured by Bruker.

For fitting, a function shown in the following <Equation 1> is used.

<Equation 1>

f(t)=R _α exp(-t/T _α )+R _β exp(-t/T _β )+R _γ exp(-t/T _γ )

(However, R _α + R _β + R _γ = 100)

t: variable (elapsed time from pulse irradiation)

T _α : relaxation time of the low-motile component α (ms)

R _α : presence ratio of low-motile component α (%)

T _β : relaxation time of intermediate component β (ms)

R _β : abundance of intermediate component β (%)

T _γ : relaxation time of high-motile component γ (ms)

R _γ : abundance of high-motile component γ (%)

Finally, from the relaxation time T and abundance ratio R obtained by curve fitting of free induction damping, the entanglement index and the intermediate component ratio are calculated by (Equation I) and (Equation II) shown below.

(entanglement index) = T _α × R _α / (R _α + R _β ) + T _β × R _β / (R _α + R _β ) (Equation I)

(middle component ratio)=R _β /(R _α +R _β ) (Equation II)

In general, in the case of a polymer in a rubbery state with active molecular chain motion, the free induction attenuation obtained by pulse NMR measurement can be represented by an exponential function. Therefore, also in this measurement, the obtained free induction attenuation can be fitted as the sum of three other components expressed by an exponential function, as shown in <Equation 1> above.

In addition, it is known that the decay rate of the free induction decay becomes slower as the ^1H motility increases, that is, as the motility of the molecular chain increases. Since the relaxation time T in each exponential function has a relationship of T _α < T _β < T _γ , the component with the lowest mobility is α, the component with intermediate mobility is β, and the component with the highest mobility is γ.

In addition, component α corresponds to a portion in which molecular chains are strongly intertwined in the polyethylene powder, component β corresponds to a portion where molecular chains are weakly intertwined, and component γ corresponds to a portion where molecular chains are not intertwined.

In this embodiment, the entanglement index and the intermediate component ratio at 180°C can be measured more specifically by the method described in Examples.

(Rate of change in the abundance ratio of low moiety components at 180 ° C.)

In the polyethylene powder of the present embodiment, in pulse NMR, the abundance ratio of the low-mobility component α at 180 ° C. The range of the rate of change of is preferably -5% or more and 10% or less, more preferably -2% or more and 8% or less, still more preferably 0% or more and 6% or less.

The rate of change in the proportion of the low-moistility component present at 180° C. in the polyethylene powder of the present embodiment is obtained by the method shown below.

When obtaining the above-mentioned (entanglement index and intermediate component ratio at 180 ° C.), the free induction attenuation (FID) obtained by the first measurement and the fourth measurement among the pulse NMR measurements specifically shown above, Curve fitting was performed using the analysis program TD-NMR-A manufactured by Bruker. For fitting, the function shown in <Equation 1> described above is used.

From the abundance ratio R obtained by fitting, the change rate (%) of the abundance ratio of the low moiety component is calculated by the following (Formula III).

(Rate of change in the abundance ratio of the low-motile component) = ((R _α4 -R _α1 )/R _α1 ) × 100 . (Equation III)

R _α1 : Abundance ratio of the low moiety component α in the first measurement

R _α4 : Abundance ratio of low moiety component α in the 4th measurement

This change rate shows a negative value when the molecular chains of the strongly entangled component are entangled under heating conditions, and shows a positive value when the molecular chains of the weakly entangled component are strongly entangled with each other.

When the rate of change in the abundance ratio of the above-described low motility component is -5% or more, components having strong entanglement tend to remain even after molding and processing, and a microporous membrane having more excellent mechanical strength and creep resistance can be obtained. On the other hand, when the rate of change in the abundance ratio of the above-described low moiety component is 10% or less, the ratio of weakly intertwined molecular chains and non-intertwined molecular chains can be maintained at a certain level or more, and molding processability tends to be excellent.

The rate of change in the proportion of the low-moistility component present in the polyethylene powder of the present embodiment at 180° C. can be specifically measured by the method described in Examples.

The rate of change in the presence ratio of the low moiety component at 180 ° C. of the polyethylene powder of the present embodiment can be controlled within the above numerical range by adjusting the concentration or temperature during synthesis of the catalyst carrier to a certain value or higher.

(Rate of change in abundance of highly motile components at 180°C)

In the polyethylene powder of the present embodiment, in pulse NMR, the abundance ratio of the highly mobile component at 180 ° C. The range of change rate is preferably 50% or less, more preferably 10% or less, still more preferably 5% or less. In addition, the lower limit is not particularly limited and is usually 0% or more.

The rate of change in the abundance of the highly mobile component in the polyethylene powder of the present embodiment is obtained by the method shown below.

When obtaining the above-mentioned (entanglement index and intermediate component ratio at 180 ° C.), the free induction attenuation (FID) obtained by the first measurement and the fourth measurement among the pulse NMR measurements specifically shown above, Curve fitting was performed using the analysis program TD-NMR-A manufactured by Bruker.

For fitting, the function shown in <Equation 1> described above is used.

From the abundance ratio R obtained by fitting, the rate of change (%) of the highly motile component shown in (Formula IV) below is calculated.

(Rate of change in abundance of high-motile components) = ((R _γ4 -R _γ1 )/R _γ1 )×100 . (Equation IV)

R _γ1 : The abundance of the highly motile component γ in the first measurement

R _γ4 : Abundance ratio of the highly motile component γ in the 4th measurement

This rate of change takes on a larger value as the entanglement of molecular chains is untied under heating conditions.

When the rate of change in the abundance of the above-described high-motility component is 50% or less, components having entangled molecular chains tend to remain even after molding and processing, and a microporous membrane having more excellent mechanical strength and creep resistance can be obtained.

The rate of change in the abundance of the highly mobile component at 180°C of the polyethylene powder of the present embodiment can be specifically measured by the method described in Examples.

The rate of change in the proportion of the highly mobile component at 180 ° C. in the polyethylene powder of the present embodiment can be controlled within the above numerical range by adjusting the concentration of the slurry during polymerization or the stirring speed to an appropriate range.

(Isothermal crystallization time at 125 ° C)

The polyethylene powder of the present embodiment has an isothermal crystallization time of preferably 5 minutes or less, more preferably 4.5 minutes or less, still more preferably 4 minutes or less.

In addition, the lower limit of the isothermal crystallization time is not particularly limited and is usually 0 minutes or more.

The isothermal crystallization time at 125 ° C. in the polyethylene powder of the present embodiment is obtained by the method shown below using a differential scanning calorimeter (DSC).

First, an aluminum pan in which polyethylene powder is sealed is placed in a heating furnace, and a heating operation is performed according to <temperature raising/lowering conditions> shown below. However, the heating operation shall be performed in a nitrogen atmosphere.

<Raising and lowering temperature conditions>

(1) Hold at 50°C for 1 minute.

(2) The temperature is raised to 180°C at a rate of 200°C/min.

(3) Hold at 180°C for 5 minutes.

(4) The temperature is lowered to 125°C at a rate of 80°C/min.

The time at which the temperature reaches 125°C is taken as the starting point (0 minute), and the time at which the peak top of the exothermic peak due to crystallization is obtained is the isothermal crystallization time at 125°C.

Since the above-mentioned isothermal crystallization time at 125 ° C. is 5 minutes or less, components having entangled molecular chains tend to exist uniformly in the molded body, so that stress propagates easily and a microporous film with more excellent creep resistance is obtained. can

As a method for controlling the isothermal crystallization time at 125 ° C. of the polyethylene powder of the present embodiment, a method of uniformly supporting the active point on the carrier of the catalyst used in the polymerization step of the polyethylene powder, or uniformly adjusting the temperature in the polymerization reactor how to do it, etc.

The isothermal crystallization time at 125°C in the polyethylene powder of the present embodiment can be specifically measured by the method described in Examples.

(viscosity average molecular weight (Mv))

The viscosity average molecular weight (Mv) of the polyethylene powder of the present embodiment is preferably 200,000 or more and 10,000,000 or less, more preferably 250,000 or more and 3,000,000 or less, still more preferably 300,000 or more and 2,000,000 or less.

The viscosity average molecular weight (Mv) of the polyethylene powder can be controlled within the above numerical range by appropriately adjusting the polymerization conditions and the like described later.

Specifically, the viscosity average molecular weight (Mv) can be controlled within the above numerical range by allowing hydrogen to exist as a chain transfer agent in the polymerization system or by changing the polymerization temperature.

The polyethylene powder of this embodiment has a viscosity average molecular weight (Mv) of 200,000 or more, so that the microporous film containing the polyethylene powder of this embodiment has sufficient mechanical strength.

On the other hand, because the viscosity average molecular weight (Mv) is 10,000,000 or less, the polyethylene powder of the present embodiment tends to be excellent in molding processability such as dispersibility in a solvent and stretchability. Therefore, the microporous membrane molded using the polyethylene powder of the present embodiment has little thickness unevenness and unmelted matter, is hard to deteriorate, and has an excellent appearance.

The viscosity average molecular weight (Mv) of the polyethylene powder of this embodiment is computable by the following formula from limiting viscosity [eta] (dL/g) calculated|required according to ISO1628-3 (2010).

More specifically, it can be measured by the method described in the Examples.

Mv=(5.34×10 ⁴ )×[η] ^1.49

(median diameter)

The polyethylene powder of the present embodiment preferably has a median diameter range of 50 µm or more and 250 µm or less, more preferably 60 µm or more and 200 µm or less, and still more preferably 70 µm or more and 150 µm or less. am.

The median diameter of the polyethylene powder of this embodiment is a particle diameter (D50) at which the cumulative mass is 50%.

When the above-mentioned median diameter is 50 μm or more, the ease of handling of the polyethylene powder in the manufacturing process or extrusion process (improvement of fluidity, suppression of dust, etc.) is improved.

On the other hand, when the median diameter is 250 µm or less, the plasticizer tends to impregnate the polyethylene powder, and the molding processability tends to be improved.

As a method of controlling the median diameter of the polyethylene powder of the present embodiment to the above numerical range, for example, a method of controlling the particle diameter of the polymerization catalyst, or a method in which the polymerization reaction rapidly proceeds (hereinafter, when described as rapid polymerization) There is a method of adjusting the polymerization conditions described later so as to suppress), etc. are mentioned.

The median diameter of the polyethylene powder of this embodiment can be specifically measured by the method described in the Example mentioned later.

[Method for producing polyethylene powder]

Below, the manufacturing method of the polyethylene powder of this embodiment is demonstrated.

(catalyst component)

The catalyst component used in the production of the ethylene-based polymer constituting the polyethylene powder of the present embodiment is not particularly limited, but is a Ziegler-Natta catalyst produced by the method described in Japanese Patent No. 5782558 or Japanese Unexamined Patent Publication No. 2019-19265 It is possible to use a metallocene catalyst. In particular, it is preferable to use a Ziegler-Natta catalyst.

As the Ziegler-Natta catalyst used for production of the polyethylene powder of the present embodiment, for example, including a solid catalyst component [A] and an organometallic compound component [B], the solid catalyst component [A] is the following (formula To a carrier (A-3) prepared by the reaction of an organomagnesium compound (A-1) soluble in an inert hydrocarbon solvent represented by i) and a chlorinating agent (A-2) represented by the following (formula ii), the following A catalyst for olefin polymerization prepared by supporting an organic magnesium compound (A-4) soluble in an inert hydrocarbon solvent represented by formula (iii) and a titanium compound (A-5) represented by formula (iv) below is preferred .

(A-1): (M ¹ ) _γ (Mg) _δ (R ¹ ) _e (R ² ) _f (OR ³ ) _g . (Formula i)

(In formula i, M ¹ is a metal atom belonging to any member selected from the group consisting of Groups 12, 13, and 14 of the periodic table, and R ¹ , R ² and R ³ are hydrocarbons each having 2 or more and 20 or less carbon atoms. is a group, and γ, δ, e, f and g are real numbers satisfying the following relationship.

0≤γ, 0<δ, 0≤e, 0≤f, 0≤g, 0<e+f, 0≤g/(γ+δ)≤2, kγ+2δ=e+f+g (where, k represents the valence of M ¹ )))

(A-2): H _h SiCl _i R ⁴ _(4-(h+i)) . (Equation ii)

(In formula ii, R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, and h and i are real numbers satisfying the following relationship: 0<h, 0<i, 0<h+i≤4)

(A-4): (M ² ) _α (Mg) _β (R ⁴ ) _a (R ⁵ ) _b Y ¹ _c . (Equation iii)

(In formula iii, M ² is a metal atom selected from the group consisting of groups 12, 13 and 14 of the periodic table, R ⁴ and R ⁵ are hydrocarbon groups having 2 or more and 20 or less carbon atoms, and Y ¹ is alkoxy, siloxy, allyloxy, amino, amide, -N=CR ⁶ , R ⁷ , -SR ⁸ (wherein R ⁶ , R ⁷ and R ⁸ represent a hydrocarbon group having 1 to 20 carbon atoms. c is In the case of 2, Y ¹ may be different from each other) and any of the β-keto acid residues, and α, β, a, b, and c are real numbers satisfying the following relationship.

0≤α, 0<β, 0≤a, 0≤b, 0≤c, 0<a+b, 0≤c/(α+β)≤2, nα+2β=a+b+c (where, n represents the valence of M ² ))

(A-5): Ti(OR ⁹ ) _d X ¹ _(4-d) . . . (Equation iv)

(In formula iv, d is a real number of 0 or more and 4 or less, R ⁹ is a hydrocarbon group having 1 or more and 20 or less carbon atoms, and X ¹ is a halogen atom.)

First, the organomagnesium compound (A-1) is described.

The organomagnesium compound (A-1) is shown as a form of a complex of organomagnesium soluble in an inert hydrocarbon solvent, but includes both dihydrocarbylmagnesium compounds and complexes of this compound and other metal compounds.

The relational expression kγ+2δ=e+f+g of the symbols γ, δ, e, f and g in the formula (i) represents the valence of the metal atom and the stoichiometry of the substituent.

In the formula (i), the hydrocarbon group represented by R ¹ and R ² is not particularly limited, and is, for example, an alkyl group, a cycloalkyl group or an aryl group each independently, such as methyl, ethyl, propyl, butyl, propyl, hexyl, octyl, decyl, cyclohexyl, phenyl groups and the like.

Among these, it is preferable that each of R ¹ and R ² is an alkyl group.

In the case of γ>0, as the metal atom M ¹ , a metal atom belonging to any of the groups consisting of groups 12, 13, and 14 of the periodic table can be used, and examples thereof include zinc, boron, and aluminum. can In particular, aluminum and zinc are preferable.

The ratio δ/γ of magnesium to the metal atom M ¹ is not particularly limited, but is preferably 0.1 or more and 30 or less, and more preferably 0.5 or more and 10 or less.

Further, as (A-1), when a predetermined organomagnesium compound with γ = 0 is used, for example, when R ¹ is 1-methylpropyl group or the like, it is soluble in an inert hydrocarbon solvent, and such a compound is also used in this embodiment. In the production of polyethylene powder in the form, it gives desirable results.

In the above formula (i), the hydrocarbon groups R ¹ and R ² when γ = 0 are preferably any of the following three groups (1), (2) and (3).

County (1):

At least one of R ¹ and R ² is a secondary or tertiary alkyl group having 4 or more and 6 or less carbon atoms. Preferably, both of R ¹ and R ² have 4 or more and 6 or less carbon atoms, and at least one is a secondary or tertiary alkyl group.

County (2):

R ¹ and R ² are alkyl groups having different carbon atoms. Preferably, R ¹ is an alkyl group having 2 or 3 carbon atoms, and R ² is an alkyl group having 4 or more carbon atoms.

County (3):

At least one of R ¹ and R ² is a hydrocarbon group having 6 or more carbon atoms. Preferably, it is an alkyl group in which the sum of carbon atoms contained in R ¹ and R ² is 12 or more.

Hereinafter, in the above (formula i), the hydrocarbon groups R ¹ and R ² in the case of γ = 0 are specifically shown.

Examples of the secondary or tertiary alkyl group having 4 or more and 6 or less carbon atoms in group (1) include 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, 2-methylbutyl, and 2-ethylpropyl. , 2,2-dimethylpropyl, 2-methylpentyl, 2-ethylbutyl, 2,2-dimethylbutyl, 2-methyl-2-ethylpropyl group, etc. are mentioned. In particular, a 1-methylpropyl group is preferable.

Moreover, as a C2 or C3 alkyl group in group (2), ethyl, 1-methylethyl, a propyl group etc. are mentioned, for example.

An ethyl group is particularly preferred.

Moreover, although it does not specifically limit as a C4 or more alkyl group, For example, a butyl, pentyl, hexyl, heptyl, an octyl group etc. are mentioned.

In particular, butyl and hexyl groups are preferable.

Moreover, although it does not specifically limit as a hydrocarbon group of 6 or more carbon atoms in group (3), For example, a hexyl, heptyl, octyl, nonyl, decyl, phenyl, 2-naphthyl group etc. are mentioned. Among the hydrocarbon groups, an alkyl group is preferable, and among the alkyl groups, hexyl and octyl groups are more preferable.

In general, as the number of carbon atoms contained in the alkyl group increases, it tends to become more soluble in inert hydrocarbon solvents, and the viscosity of the solution tends to increase. Therefore, in the above (formula i), it is preferable to use an appropriate long-chain alkyl group as the hydrocarbon groups R ¹ and R ² from the viewpoint of handling. The organomagnesium compound (A-1) is used as an inert hydrocarbon solution, but it can be used without any problems even if a small amount of Lewis basic compounds such as ethers, esters, and amines are contained or remain in the solution.

Next, the alkoxy group (OR ³ ) in (formula i) of the organomagnesium compound (A-1) will be described.

As the hydrocarbon group represented by R ³ , an alkyl group or aryl group having 1 or more and 12 or less carbon atoms is preferable, and an alkyl group or aryl group having 3 or more and 10 or less carbon atoms is more preferable.

R ³ is not particularly limited, and examples thereof include methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 1,1-dimethylethyl, pentyl, hexyl, 2-methylpentyl, and 2-ethyl. butyl, 2-ethylpentyl, 2-ethylhexyl, 2-ethyl-4-methylpentyl, 2-propylheptyl, 2-ethyl-5-methyloctyl, octyl, nonyl, decyl, phenyl, naphthyl groups and the like. .

In particular, butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl groups are more preferable.

The synthesis method of the organomagnesium compound (A-1) is not particularly limited. For example, formula: R ¹ MgX ¹ and formula: R ¹ ₂ Mg (R ¹ is as described above, X ¹ is a halogen atom. ) consisting of any organomagnesium compound belonging to the group consisting of Formula: M ¹ R ² _k and Formula: M ¹ R ² _(k-1) H (M ¹ , R ² and k are as described above). An organometallic compound belonging to the group is reacted in an inert hydrocarbon solvent at a temperature of 25°C or more and 150°C or less, and if necessary, continues to have a hydrocarbon group represented by R ² (R ² is as described above). A method of synthesizing by reacting with an alkoxymagnesium compound having a hydrocarbon group represented by R ² soluble in alcohol or an inert hydrocarbon solvent and/or an alkoxy aluminum compound is exemplified.

Among the methods described above, in the case of reacting an organomagnesium compound soluble in an inert hydrocarbon solvent with an alcohol, the order of the reaction is not particularly limited. Either method of adding or adding both at the same time can be used.

The reaction ratio between an organomagnesium compound soluble in an inert hydrocarbon solvent and an alcohol is not particularly limited, but the molar composition ratio of alkoxy groups to all metal atoms in the organomagnesium compound containing an alkoxy group obtained as a result of the reaction: g/( γ+δ) is 0≤g/(γ+δ)≤2, and preferably 0≤g/(γ+δ)<1.

Next, the chlorinating agent (A-2) is explained.

The chlorinating agent (A-2) is a silicon chloride compound represented by (formula ii), at least one of which has a Si-H bond.

(A-2): H _h SiCl _i R ⁴ _(4-(h+i)) . (Equation ii)

(In formula ii, R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, and h and i are real numbers satisfying the following relationship: 0<h, 0<i, 0<h+i≤4)

In the above (formula ii), the hydrocarbon group represented by R ⁴ is not particularly limited, and examples thereof include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Specifically, methyl, ethyl, propyl, 1-methylethyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl groups and the like.

In particular, an alkyl group having 1 to 10 carbon atoms is preferable, and an alkyl group having 1 to 3 carbon atoms such as methyl, ethyl, propyl, and 1-methylethyl group is more preferable. Further, h and i are numbers greater than 0 that satisfy the relationship h+i≤4, and i is preferably 2 or more and 3 or less.

Examples of the chlorinating agent (A-2) include, but are not particularly limited to, HSiCl ₃ , HSiCl ₂ CH ₃ , HSiCl ₂ C ₂ H ₅ , HSiCl ₂ (C ₃ H ₇ ), HSiCl ₂ (2-C ₃ H ₇ ), HSiCl ₂ (C4H ₉ ), HSiCl ₂ (C ₆ H ₅ ), HSiCl ₂ (4-Cl-C ₆ H4), HSiCl ₂ (CH=CH ₂ ), HSiCl ₂ (CH ₂ C ₆ H ₅ ) , HSiCl ₂ (1-C ₁₀ H ₇ ), HSiCl ₂ (CH ₂ CH=CH ₂ ), H ₂ SiCl(CH ₃ ), H ₂ SiCl(C ₂ H ₅ ), HSiCl(CH ₃ ) ₂ , HSiCl( _{and the like . _ _ _ _ _ _ _ _}

As the chlorinating agent (A-2), a silicon chloride compound containing these compounds or a mixture of two or more selected from these compounds is used.

In particular, HSiCl ₃ , HSiCl ₂ CH ₃ , HSiCl(CH ₃ ) ₂ , and HSiCl ₂ (C ₃ H ₇ ) are preferable, and HSiCl ₃ and HSiCl ₂ CH ₃ are more preferable.

Next, the reaction between the organomagnesium compound (A-1) and the chlorinating agent (A-2) will be described.

During the reaction, the chlorinating agent (A-2) is previously mixed with an inert hydrocarbon solvent, chlorinated hydrocarbons such as 1,2-dichloroethane, o-dichlorobenzene and dichloromethane, ether solvents such as diethyl ether and tetrahydrofuran, or It is preferable to use after diluting with these mixed solvents. Among these, it is more preferable to use an inert hydrocarbon solvent in view of catalyst performance.

The reaction ratio between the organomagnesium compound (A-1) and the chlorinating agent (A-2) is not particularly limited, but the ratio of the silicon atoms contained in (A-2) to 1 mol of magnesium atoms contained in (A-1) The number of moles is preferably 0.01 mol or more and 100 mol or less, and more preferably 0.1 mol or more and 10 mol or less.

There is no particular restriction on the reaction method between the organomagnesium compound (A-1) and the chlorinating agent (A-2), and a simultaneous addition method in which (A-1) and (A-2) are reacted while simultaneously introducing them into the reactor; A method in which (A-2) is introduced into a reactor in advance and then (A-1) is introduced into a reactor, or a method in which (A-1) is introduced into a reactor in advance and then (A-2) is introduced into a reactor Any of the methods can be used.

In particular, a method in which (A-1) is introduced into the reactor after introducing (A-2) into the reactor in advance is preferable.

The carrier (A-3) obtained by the above reaction is preferably separated by filtration or decantation and then thoroughly washed with an inert hydrocarbon solvent to remove unreacted substances or by-products.

The reaction temperature between the organomagnesium compound (A-1) and the chlorinating agent (A-2) is not particularly limited, but is 75°C or higher and 150°C from the viewpoint of increasing the pores of the carrier (A-3) and making it brittle. It is preferably less than or equal to, more preferably 80°C or more and 120°C or less, and still more preferably 80°C or more and 100°C or less.

In the simultaneous addition method in which (A-1) and (A-2) are introduced into a reactor and reacted simultaneously, the temperature of the reactor is adjusted to a predetermined temperature in advance, and the temperature in the reactor is adjusted to a predetermined temperature while performing simultaneous addition. It is desirable to do

In the method in which (A-2) is introduced into the reactor in advance and then (A-1) is introduced into the reactor, the temperature of the reactor into which the chlorinating agent (A-2) is charged is adjusted to a predetermined temperature, and organomagnesium It is preferable to adjust the temperature in the reactor to a predetermined temperature while introducing the compound (A-1) into the reactor.

In the method in which (A-2) is introduced into the reactor after previously introducing (A-1) into the reactor, the temperature of the reactor into which (A-1) is introduced is adjusted to a predetermined temperature, and (A-2) It is preferable to adjust the temperature in the reactor to a predetermined temperature while introducing into the reactor.

The concentration (magnesium concentration) of (A-1) in the reaction system of the organomagnesium compound (A-1) and the chlorinating agent (A-2) is not particularly limited, but the pores of the carrier (A-3) are increased, , From the viewpoint of making cracking easier, it is preferably 0.8 mol/L or more and 2.5 mol/L or less, and more preferably 1.0 mol/L or more and 2.0 mol/L or less.

Next, the organomagnesium compound (A-4) is described.

As (A-4), what is represented by the above-mentioned (formula iii) is preferable.

(A-4): (M ² ) _α (Mg) _β (R ⁴ ) _a (R ⁵ ) _b Y ¹ _c . (Equation iii)

(In formula iii, M ² is a metal atom selected from the group consisting of groups 12, 13 and 14 of the periodic table, R ⁴ and R ⁵ are hydrocarbon groups having 2 or more and 20 or less carbon atoms, and Y ¹ is alkoxy, siloxy, allyloxy, amino, amide, -N=CR ^6, R ⁷ , -SR ⁸ (wherein R ⁶ , R ⁷ and R ⁸ represent a hydrocarbon group having 1 to 20 carbon atoms. c is In the case of 2, Y ¹ may be different from each other) and any of the β-keto acid residues, and α, β, a, b, and c are real numbers satisfying the following relationship.

0≤α, 0<β, 0≤a, 0≤b, 0≤c, 0<a+b, 0≤c/(α+β)≤2, nα+2β=a+b+c (where, n represents the valence of M ² ))

The amount of the organomagnesium compound (A-4) used is such that the molar ratio of magnesium atoms contained in the organomagnesium compound (A-4) to titanium atoms contained in the titanium compound (A-5) is Mg/Ti=0.1 or more. It is preferably 10 or less, and more preferably 0.5 or more and 5 or less.

The temperature of the reaction between the organomagnesium compound (A-4) and the titanium compound (A-5) is not particularly limited, but is preferably -80°C or higher and 150°C or lower, and more preferably -40°C or higher and 100°C or lower. .

The concentration at the time of use of the organomagnesium compound (A-4) is not particularly limited, but is preferably 0.1 mol/L or more and 2 mol/L or less, based on the magnesium atoms contained in the organomagnesium compound (A-4), and 0.5 mol It is more preferable that they are /L or more and 1.5 mol/L or less. In addition, it is preferable to use an inert hydrocarbon solvent for dilution of the organomagnesium compound (A-4).

Next, the titanium compound (A-5) will be described.

As described above, the titanium compound (A-5) is a titanium compound represented by the following formula iv.

(A-5): Ti(OR ⁹ ) _d X ¹ _(4-d) . . . (Equation iv)

(In formula iv, d is a real number of 0 or more and 4 or less, R ⁹ is a hydrocarbon group having 1 or more and 20 or less carbon atoms, and X ¹ is a halogen atom.)

In the above (formula iv), it is preferable that d is 0 or more and 1 or less, and it is more preferable that d is 0.

The hydrocarbon group represented by R ⁹ in (Formula iv) is not particularly limited, and examples thereof include methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, and allyl groups. Of the aliphatic hydrocarbon group; alicyclic hydrocarbon groups such as cyclohexyl, 2-methylcyclohexyl, and cyclopentyl groups; Aromatic hydrocarbon groups, such as a phenyl and a naphthyl group, etc. are mentioned. In particular, an aliphatic hydrocarbon group is preferred.

The halogen represented by X ¹ is not particularly limited, and examples thereof include chlorine, bromine and iodine. In particular, chlorine is preferred.

A titanium compound (A-5) may be used individually by 1 type, or may be used in mixture of 2 or more types.

The amount of titanium compound (A-5) used is not particularly limited, but from the viewpoint of increasing the supported amount in the pores of the support, the molar ratio of titanium to magnesium atoms contained in the support (A-3) (Ti/Mg) , 0.15 or more and 20 or less are preferable, and 0.2 or more and 10 or less are more preferable.

The reaction temperature of the titanium compound (A-5) is not particularly limited, but is preferably -80°C or higher and 150°C or lower, and more preferably -40°C or higher and 100°C or lower.

The method of supporting the titanium compound (A-5) on the carrier (A-3) is not particularly limited, and a method of reacting an excess titanium compound (A-5) with respect to the carrier (A-3), or a third component By using, you may use the method of carrying|supporting titanium compound (A-5) efficiently. In particular, a method in which the titanium compound (A-5) and the organomagnesium compound (A-4) are reacted to be supported on the carrier (A-3) is preferable.

The order of addition of the organomagnesium compound (A-4) and the titanium compound (A-5) to the carrier (A-3) is not particularly limited, and the organomagnesium compound (A-4) is followed by the titanium compound (A-5). , adding the organomagnesium compound (A-4) after the titanium compound (A-5), or adding the organomagnesium compound (A-4) and the titanium compound (A-5) at the same time. can also

In particular, a method of simultaneously adding the organomagnesium compound (A-4) and the titanium compound (A-5) is preferable.

The reaction between the organomagnesium compound (A-4) and the titanium compound (A-5) is carried out in an inert hydrocarbon solvent, but an aliphatic hydrocarbon solvent such as hexane or heptane is preferably used.

The catalyst obtained as described above is used as a slurry solution using an inert hydrocarbon solvent.

When transferring the slurry solution, from the viewpoint of preventing the obtained catalyst from cracking during the polymerization process, it is preferable to add a thickener or control the pressure difference between the transfer source and the transfer destination to be small.

The thickener is not particularly limited, but from the viewpoint of maintaining the performance of the catalyst, saturated hydrocarbons are preferable, and specific examples thereof include liquid paraffin and polyolefin wax.

The pressure difference between the transfer source and the transfer destination is not particularly limited, but is preferably 0.1 MPa or more and 0.5 MPa or less, and more preferably 0.1 MPa or more and 0.3 MPa or less.

Next, the organometallic compound component [B] used as a catalyst component in the polymerization of the polyethylene powder of the present embodiment will be described.

As a catalyst used for polymerization of the polyethylene powder of the present embodiment, a highly active solid catalyst for polymerization is obtained by combining the above-described solid catalyst component [A] and organometallic compound component [B].

The organometallic compound component [B] is sometimes called a "co-catalyst".

The organometallic compound component [B] is preferably a compound containing any metal belonging to the group consisting of Group 1, Group 2, Group 12 and Group 13 of the periodic table, and in particular, an organoaluminium compound and/or organomagnesium. compounds are preferred.

As an organoaluminum compound, it is preferable to use the compound represented by the following (formula v) individually or in mixture.

AlR ¹⁰ _j Z ¹ _(3-j) . . . (Equation v)

(In Formula V, R ¹⁰ is a hydrocarbon group having 1 or more and 20 or less carbon atoms, Z ¹ is any group belonging to the group consisting of hydrogen, halogen, alkoxy, allyloxy, and siloxy groups, and j is a number of 2 or more and 3 or less. .)

In the formula (v), the hydrocarbon group represented by R ¹⁰ having 1 to 20 carbon atoms is not particularly limited, and examples thereof include those containing aliphatic hydrocarbons, aromatic hydrocarbons, and alicyclic hydrocarbons. As, trimethyl aluminum, triethyl aluminum, tripropyl aluminum, tributyl aluminum, tri (2-methylpropyl) aluminum (or triisobutyl aluminum), tripentyl aluminum, tri (3-methylbutyl) aluminum, trihexyl trialkyl aluminum such as aluminum, trioctyl aluminum, and tridecyl aluminum; halogenated aluminum compounds such as diethyl aluminum chloride, ethyl aluminum dichloride, bis(2-methylpropyl) aluminum chloride, ethyl aluminum sesquichloride, and diethyl aluminum bromide; alkoxy aluminum compounds such as diethyl aluminum ethoxide and bis(2-methylpropyl) aluminum butoxide; Siloxy aluminum compounds such as dimethylhydrosiloxyaluminumdimethyl, ethylmethylhydrosiloxyaluminumdiethyl, and ethyldimethylsiloxyaluminumdiethyl, and mixtures thereof are mentioned as preferred examples.

In particular, a trialkyl aluminum compound is more preferable.

As the organomagnesium compound, an organomagnesium compound soluble in an inert hydrocarbon solvent represented by the formula (formula i) is preferable.

Although γ, δ, e, f, g, M ^{1 ,} R ¹ , R ² , and OR ³ in the formula (i) have already been described, this organomagnesium compound has high solubility in inert hydrocarbon solvents. Since one is preferable, β/α is preferably in the range of 0.5 to 10, and a compound in which M ¹ is aluminum is more preferable.

The method of adding the solid catalyst component [A] and organometallic compound component [B] into the polymerization system under polymerization conditions is not particularly limited, and both may be separately added into the polymerization system, or after reacting both in advance, the polymerization system may be added within.

In addition, although the ratio of both to be combined is not particularly limited, it is preferable that the organic metal compound component [B] be 1 mmol or more and 3000 mmol or less with respect to 1 g of the solid catalyst component [A].

(Polymerization method of ethylene-based polymer)

Examples of the polymerization method of the ethylene-based polymer constituting the polyethylene powder of the present embodiment include a method of polymerizing ethylene or copolymerizing ethylene and a comonomer by a suspension polymerization method or a gas phase polymerization method.

Among these, a suspension polymerization method capable of efficiently removing heat from polymerization is preferred.

In the suspension polymerization method, an inert hydrocarbon medium can be used as a solvent, and olefin itself can also be used as a solvent.

Examples of the inert hydrocarbon medium include, but are not particularly limited to, aliphatic hydrocarbons such as propane, butane, isobutane, pentane, isopentane, hexane, heptane, octane, decane, dodecane, and kerosene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; Aromatic hydrocarbons, such as benzene, toluene, and xylene; and halogenated hydrocarbons such as ethyl chloride, chlorobenzene, and dichloromethane, or mixtures thereof.

In the polymerization of the ethylene-based polymer in the polyethylene powder production method of the present embodiment, the method for adding the above-described [catalyst component] into the polymerization reactor is not particularly limited, but a component having strong molecular chains entangled It is preferable to add a [catalyst component] preliminarily polymerized in advance from the viewpoint of polymerization within the catalyst pores and from the viewpoint of making the catalyst easily cracked in the polymerization system.

The polymerization temperature of the ethylene-based polymer in the polyethylene powder production method of the present embodiment is preferably 40°C or more and 100°C or less, more preferably 45°C or more and 95°C or less, and even more preferably 50°C or more ° C or higher and 90 ° C or lower.

When the polymerization temperature is 40°C or higher, industrially efficient production becomes possible. On the other hand, when the polymerization temperature is 100°C or less, bulky scale generated by melting of a part of the polymer can be suppressed, and continuous and stable production is possible without clogging of the piping.

The polymerization pressure of the ethylene-based polymer in the polyethylene powder manufacturing method of the present embodiment is preferably normal pressure or higher and 2 MPaG or lower, more preferably 0.2 MPaG or higher and 1.5 MPaG or lower, still more preferably 0.3 MPaG or higher It is 0.9 MPaG or less.

When the polymerization pressure is equal to or higher than normal pressure, industrially efficient production becomes possible. On the other hand, when the polymerization pressure is 2 MPaG or less, stable production tends to be possible without generating bulky scale due to rapid polymerization in the polymerization reactor.

In general, when polymerizing an ethylene-based polymer, an antistatic agent such as Stadis or STATSAFE manufactured by Innospec Co. (available from Maru and Bussan) may be used to suppress the polymer's static adhesion to the polymerization reactor.

An antistatic agent such as Stadis or STATSAFE can be diluted in an inert hydrocarbon medium and added to the polymerization reactor by means of a pump or the like. The addition of the antistatic agent can be performed by a method of adding to a solid catalyst in advance or by a method of adding to a polymerization reactor, and the addition amount is preferably 1 ppm or more and 500 ppm or less with respect to the amount of ethylene-based polymer produced per unit time , 10 ppm or more and 100 ppm or less are more preferable.

As described in West German Patent Application Laid-open No. 3127133, the molecular weight of the ethylene-based polymer can be adjusted by making hydrogen present in the polymerization system or by changing the polymerization temperature.

Specifically, by adding hydrogen as a chain transfer agent into the polymerization system, the molecular weight of the ethylene polymer can be controlled within an appropriate range. When hydrogen is added into the polymerization system, the range of the mole fraction of hydrogen is preferably 0 mol% or more and 30 mol% or less, and more preferably 0 mol% or more and 25 mol% or less.

Further, hydrogen may be added into the polymerization system from the catalyst introduction line after contacting with the catalyst in advance. Immediately after the catalyst is introduced into the polymerization system, since the concentration of the catalyst in the vicinity of the outlet of the inlet line is high, rapid polymerization proceeds and the possibility of local high-temperature conditions increases. On the other hand, by contacting hydrogen and the catalyst before introduction into the polymerization system, the initial activity of the catalyst can be suppressed, and the generation of bulky scale due to rapid polymerization or the deactivation of the catalyst at high temperatures can be suppressed.

The concentration range of the polymerization slurry in the method for producing the ethylene-based polymer constituting the polyethylene powder of the present embodiment is preferably 30% by mass or more and 60% by mass or less, from the viewpoint of making the catalyst easily cracked in the polymerization system. and more preferably 40% by mass or more and 50% by mass or less.

The range of the stirring speed in the method for producing the ethylene-based polymer constituting the polyethylene powder of the present embodiment is preferably 300 rpm or more and 600 rpm or less, more preferably from the viewpoint of making the catalyst easily cracked in the polymerization system. It is 400 rpm or more and 500 rpm or less.

The polymerization reaction may be carried out in any of a batch, semi-continuous and continuous manner, preferably in a continuous manner.

By continuously supplying ethylene gas, a solvent, a catalyst, etc. into the polymerization system and continuously discharging it together with the produced ethylene polymer, it is possible to suppress a partial high-temperature state due to rapid ethylene reaction and further stabilize the polymerization system. When ethylene reacts in a uniform state in the system, the formation of branches, double bonds, etc. in the polymer chain is suppressed, or the formation of low-molecular-weight components and ultra-high molecular weight substances due to decomposition or crosslinking of the ethylene polymer is suppressed, resulting in ethylene The crystalline component of the polymer becomes more likely to be formed. This makes it easier to obtain a crystalline component in an amount necessary and sufficient for strength in a film or microporous film using the polyethylene powder of the present embodiment.

In addition, the polymerization reaction may be a single-stage polymerization method using one polymerization reactor, or a multi-stage polymerization method in which polymerization is performed sequentially and continuously with two or more polymerization reactors connected in series.

Production of the ethylene-based polymer using the multistage polymerization method is specifically performed by the method shown below.

First, the ethylene-based polymer X is prepared in the polymerization reactor of the first stage using the above-described production conditions, and the ethylene-based polymer X extracted from the polymerization reactor of the first stage is transferred to the intermediate flash tank, and the unreacted ethylene, hydrogen, and comonomers (limited to the case where copolymerization is performed in the polymerization reactor of the first stage) are separated. Then, the suspension containing the ethylene-based polymer X is transferred to the second-stage polymerization reactor, and the ethylene-based polymer Y is produced using the production conditions described above.

The range of the polymerization pressure in the first-stage polymerization reactor is preferably 0.6 MPaG or more and 2.0 MPaG or less, more preferably from the viewpoint of polymerizing a component having a strong molecular chain entanglement within the pores of the catalyst. It is 0.7 MPaG or more and 1.5 MPaG or less, and more preferably 0.8 MPaG or more and 1.0 MPaG or less.

The concentration range of the polymerization slurry in the first-stage polymerization reactor is preferably 10% by mass or more and 30% by mass or less, from the viewpoint of controlling the catalyst from cracking in the first-stage polymerization reactor, More preferably, they are 10 mass % or more and 20 mass % or less.

The range of the stirring speed in the first-stage polymerization reactor is preferably 100 rpm or more and 300 rpm or less, more preferably 150 rpm or more, from the viewpoint of controlling the catalyst not to crack in the first-stage polymerization reactor. less than 250 rpm.

The concentration range of the polymerization slurry in the second stage polymerization reactor is preferably 30 mol% or more and 60 mol% or less, more preferably 40 mol% or more, from the viewpoint of making the catalyst easily cracked in the polymerization system. It is 50 mol% or less.

The range of the stirring speed in the second-stage polymerization reactor is preferably 300 rpm or more and 600 rpm or less, more preferably 400 rpm or more and 500 rpm or less, from the viewpoint of making the catalyst easily cracked in the polymerization system.

The ratio of the ethylene-based polymer X contained in the polyethylene powder produced by the above-described multi-stage polymerization method, that is, the range of production in the first-stage polymerization reactor, is controlled so that the catalyst is split in the second-stage polymerization reactor From the viewpoint of doing, it is preferably 10 mass% or more and 50 mass% or less, more preferably 15 mass% or more and 45 mass% or less, and still more preferably 20 mass% or more and 40 mass% or less.

As each physical property value of the ethylene-based polymer Y, the viscosity average molecular weight and density are measured after measuring the physical property values of the ethylene-based polymer X extracted from the polymerization reactor of the first stage and the polyethylene powder finally produced, in each polymerization reactor From the production volume, it can be obtained based on causticity.

The suspension containing the ethylene-based polymer constituting the polyethylene powder of the present embodiment is quantitatively extracted from the polymerization reactor, transferred to a flash tank, and unreacted ethylene, hydrogen, and comonomer (limited to the case of copolymerization in the reactor) do) is separated.

As the solvent separation method in the polyethylene powder polymerization step of the present embodiment, a decantation method, a centrifugal separation method, a filter filtration method, etc. can all be applied, but a centrifugal separation method with high separation efficiency between the ethylene-based polymer and the solvent is more preferable.

Although the method of deactivating the catalyst used in the polymerization step of the ethylene-based polymer constituting the polyethylene powder of the present embodiment is not particularly limited, it is preferable to perform the deactivation of the catalyst after separating the ethylene-based polymer and the solvent.

By introducing an agent for deactivating the catalyst after separating the polyethylene powder from the solvent, it is possible to suppress precipitation of low molecular weight components and catalyst components contained in the solvent in the ethylene-based polymer.

Examples of the agent that deactivates the catalyst include oxygen, water, alcohols, glycols, phenols, carbon monoxide, carbon dioxide, ethers, carbonyl compounds, and alkynes.

In the method for producing the polyethylene powder of the present embodiment, it is preferable to perform a drying step after separating the ethylene-based polymer from the solvent. In the drying process, it is preferable to use a rotary kiln method, a paddle method, a fluidized dryer, or the like. Further, the drying temperature is preferably 50°C or higher and 150°C or lower, and more preferably 70°C or higher and 110°C or lower.

It is also effective to promote drying by introducing an inert gas such as nitrogen into the dryer. At that time, a method of entraining steam or the like as an agent for deactivating the catalyst is also effective.

After drying the ethylene-based polymer constituting the polyethylene powder of the present embodiment, it may be sieved to remove coarse powder.

The polyethylene powder of this embodiment may be a mixture of a plurality of polyethylene powders containing the ethylene-based polymer obtained by the above-described production method.

Moreover, you may use in combination with well-known additives, such as a slip agent, a neutralizer, antioxidant, a light stabilizer, an antistatic agent, and a pigment, as needed.

Examples of the slip agent or neutralizer include, but are not particularly limited to, aliphatic hydrocarbons, higher fatty acids, metal salts of higher fatty acids, fatty acid esters of alcohols, waxes, higher fatty acid amides, silicone oil, and rosin. Specifically, stearates, such as calcium stearate, magnesium stearate, and zinc stearate, are mentioned as suitable additives.

Although it does not specifically limit as an antioxidant, For example, a phenol type compound or a phenol phosphoric acid type compound is preferable. Specifically, 2,6-di-t-butyl-4-methylphenol (dibutylhydroxytoluene), n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl) phenolic antioxidants such as propionate and tetrakis(methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate))methane; 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenzo[d,f][1,3, 2] phenol phosphorus antioxidants such as dioxaphosphepine; Tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene-di-phosphonite, tris(2,4-di-t-butylphenyl)phosphite, cyclic neopentane and phosphorus antioxidants such as tetraylbis(2,4-t-butylphenylphosphite).

Although it does not specifically limit as a light stabilizer, For example, 2-(5-methyl-2-hydroxyphenyl) benzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)- benzotriazole-based light stabilizers such as 5-chlorobenzotriazole; Bis(2,2,6,6-tetramethyl-4-piperidine)sebacate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine -2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl) imino}] and hindered amine-based light stabilizers.

Although it does not specifically limit as an antistatic agent, For example, aluminosilicate, kaolin, clay, natural silica, synthetic silica, silicates, talc, diatomaceous earth, etc., a glycerol fatty acid ester, etc. are mentioned.

〔Usage〕

The polyethylene powder of the present embodiment can be used as a raw material for various molded products such as microporous films, fibers, particularly high-strength fibers, sintered bodies, press-formed bodies, and ram extrusion molded bodies.

In particular, it is suitable as a raw material for microporous membranes for battery separators.

[molded body]

The molded body of this embodiment is a molded body of the polyethylene powder of this embodiment described above.

Examples of the molded article include a microporous film, particularly a microporous film that is a battery separator, a fiber, particularly a high-strength fiber, a sintered body, a press-formed body, and a ram extrusion molded body.

Examples of the method for producing a molded body include a molding method in which resin extrusion using a wet extrusion method, stretching, extraction, and drying steps are performed.

As the separator for batteries mentioned above, a separator for lithium ion secondary batteries, a separator for lead storage batteries, and the like are exemplified.

Example

Although the present embodiment will be described in more detail below with reference to specific examples and comparative examples, the present invention is not limited at all by the following examples and comparative examples.

First, a method for evaluating physical properties of polyethylene powder will be described.

[Physical properties of polyethylene powder]

(entanglement index and intermediate component ratio at 180 ° C)

First, a sample tube filled with polyethylene powder to a height of 1 cm from the bottom was put into a Bruker TD-NMR apparatus (model: minispec mq20) set so that the internal temperature of the sample tube was 30 ° C. The temperature of the sample tube was raised according to the conditions>.

The temperature shown in the following <temperature rising condition> is a value obtained by measuring the internal temperature of the sample with a thermocouple.

<Temperature Raising Conditions>

(1) Set to 30 degreeC, and leave still for 5 minutes.

(2) The temperature is raised to 180°C at a rate of 5°C/min.

(3) After heating up to 180°C, it is left still for 25 minutes.

After completion of the temperature increase in the above-described procedure, the spin-spin relaxation time (T ₂ , sometimes simply referred to as “relaxation time” in the present specification) of the sample was measured according to <measurement conditions> shown below.

In addition, after completion of the measurement, the same measurement was repeated three times, and the measurement was performed four times in total.

<Measurement conditions>

Magnetic Field Strength: 0.47T

Measurement nuclide: ¹ H (20 MHz)

Measurement method: Carr Purcell Meiboom Gill method

Total number of times: 256 times

Repeat time: 3 seconds

Interval between first 90° and 180° pulses (τ): 0.04 milliseconds

Total number of echo signals: 6400

Of the four measurements described above, curve fitting was performed on the free induction decay (FID) obtained by the fourth measurement using TD-NMR-A, an analysis program manufactured by Bruker.

For fitting, a function shown in the following <Equation 1> was used.

<Equation 1>

f(t)=R _α exp(-t/T _α )+R _β exp(-t/T _β )+R _γ exp(-t/T _γ )

(However, R _α + R _β + R _γ = 100)

t: variable (elapsed time from pulse irradiation)

T _α : relaxation time of the low-motile component α (ms)

R _α : presence ratio of low-motile component α (%)

T _β : relaxation time of intermediate component β (ms)

R _β : abundance of intermediate component β (%)

T _γ : relaxation time of high-motile component γ (ms)

R _γ : abundance of high-motile component γ (%)

Finally, the entanglement exponent (ms) and the intermediate component ratio were calculated from the relaxation time T and the abundance ratio R obtained by curve fitting of free induction damping, and from (Formula I) and (Formula II) shown below.

(entanglement index) = T _α × R _α / (R _α + R _β ) + T _β × R _β / (R _α + R _β ) ... (Equation I)

(intermediate component ratio)=R _β /(R _α +R _β ) … (Equation II)

(Rate of change in the abundance ratio of the low moiety component at 180 ° C.)

Among pulse NMR measurements when obtaining the above-mentioned (entanglement index and intermediate component ratio at 180 ° C.), for the free induction decay (FID) obtained by the first and fourth measurements, analysis program TD- made by Bruker Co., Ltd. Curve fitting was performed using NMR-A.

For fitting, the function shown in <Equation 1> described above was used.

From the abundance ratio R obtained by fitting, the rate of change (%) in the abundance ratio of the low moiety component was calculated from (Formula III) shown below.

(Rate of change in the abundance of the low-motile component) = ((R _α4 -R _α1 ) / R _α1 ) × 100 .(Equation III)

R _α1 : Presence ratio (%) of low moiety component α in the first measurement

R _α4 : Abundance ratio of low moiety component α in the fourth measurement (%)

(Rate of change in abundance of highly motile components at 180°C)

Among pulse NMR measurements when obtaining the above-mentioned (entanglement index and intermediate component ratio at 180 ° C.), for the free induction decay (FID) obtained by the first and fourth measurements, analysis program TD- made by Bruker Co., Ltd. Curve fitting was performed using NMR-A.

For fitting, the function shown in <Equation 1> was used.

From the abundance ratio R obtained by fitting, the rate of change (%) in the abundance ratio of the highly motile component was calculated from (Formula IV) shown below.

(Rate of change in abundance of high-motile components) = ((R _γ4 -R _γ1 )/R _γ1 )×100 . (Equation IV)

R _γ1 : Abundance ratio of the highly motile component γ in the first measurement (%)

R _γ4 : Abundance ratio (%) of the highly motile component γ in the 4th measurement

[Isothermal crystallization time]

The isothermal crystallization time of the polyethylene powder at 125°C was determined by the method shown below using a differential scanning calorimeter (product name: DSC8000, manufactured by PerkinElmer).

First, an aluminum pan in which 8.5 mg of polyethylene powder was sealed was placed in a heating furnace in the DSC apparatus, and heating was performed according to <conditions for raising and lowering the temperature> shown below.

However, all heating operations were performed under a nitrogen atmosphere.

<Raising and lowering temperature conditions>

(1) Hold at 50°C for 1 minute.

(2) The temperature is raised to 180°C at a rate of 200°C/min.

(3) Hold at 180°C for 5 minutes.

(4) The temperature is lowered to 125°C at a rate of 80°C/min.

The time at which the temperature reached 125°C was taken as the starting point (0 minutes), and the time at which the peak top of the exothermic peak due to crystallization was obtained was taken as the isothermal crystallization time (minutes) at 125°C.

(viscosity average molecular weight (Mv))

The viscosity average molecular weight of polyethylene powder was measured by the method shown below according to ISO1628-3 (2010).

First, polyethylene powder was weighed within the range of 4.0 to 4.5 mg in a melting tube. The weighed mass is expressed as "m (unit: mg)" in the following formula. Subsequently, the air inside the dissolution tube was degassed with a vacuum pump and replaced with nitrogen, and then 20 mL of decahydronaphthalene (2,6-di-t-butyl-4-methylphenol was replaced with 1 g of degassed with a vacuum pump and replaced with nitrogen). /L added, hereinafter referred to as decalin) was added, and stirred at 150°C for 90 minutes to dissolve the polyethylene powder to obtain a decalin solution.

Thereafter, the decalin solution was put into a Canon-Fenske viscometer (manufactured by Shibata Chemical Industry Co., Ltd./Viscometer No.: 100) in a constant temperature bath at 135° C., and the falling time (ts) between marked lines was measured.

In addition, the falling time (tb) of decalin alone without polyethylene powder as a blank was measured, and the specific viscosity (ηsp) was determined according to the following (Formula A).

ηsp=(ts/tb)-1 (Equation A)

Intrinsic viscosity IV was calculated from specific viscosity (ηsp) and concentration (C) (unit: g/dL) using the following (Equation B) and (Equation C).

Concentration C=m/(20×γ)/10 (unit: g/dL) (Equation B)

γ = (density of decalin at 20°C)/(density of decalin at 135°C)

=0.888/0.802=1.107

Intrinsic Viscosity IV=(ηsp/C)/(1+0.27×ηsp) (Equation C)

This intrinsic viscosity IV was substituted into the following (Formula D) to obtain the viscosity average molecular weight (Mv).

Viscosity Average Molecular Weight (Mv)=(5.34×10 ⁴ )×[η] ^1.49 (Equation D)

(median diameter)

The median diameter of the polyethylene powder was determined by the method shown below.

The polyethylene powder was classified through a sieve conforming to JIS Z8801 standard. The size of the opening of the sieve was 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm and 53 μm, and the mass of the polyethylene powder recovered for each fraction was measured. And the fraction (mass %) of each fraction with respect to the total mass of the polyethylene powder before classification was computed, and the integrated body weight ratio (mass %) was calculated|required. A particle size distribution graph, that is, a particle size distribution integration curve (integration curve from small particles) is drawn with the value of eye size as the horizontal axis and the integrated body weight ratio as the vertical axis, and the particle diameter at which the integrated body weight ratio is 50% (D50 (μm)) was taken as the median diameter.

[Method for producing microporous membrane]

Pentaerythrityl-tetrakis-[3-(3,5-di-t-butyl-4-hydroxyphenyl) propio- nate] was added at 1 part by mass and dry blended using a tumbler blender to obtain a powder mixture.

After performing nitrogen substitution, the obtained powder mixture was injected|thrown-in through the feeder in a nitrogen atmosphere to the twin-screw extruder.

Further, liquid paraffin (P-350P (trademark) manufactured by Moresco Co., Ltd.) weighed so that the total amount with polyethylene powder is 100 parts by mass is injected into a twin-screw extruder as a side feed, kneaded under 200°C conditions, and placed at the tip of the extruder. After extruding from the installed T-die, it was immediately cooled and solidified with a cast roll cooled to 25°C, and molded into a gel-like sheet having a thickness of 1200 µm. This gel-like sheet was stretched 7×7 times using a simultaneous biaxial stretching machine at 115 to 125° C. to obtain a stretched film. Thereafter, the stretched film was immersed in methyl ethyl ketone for 30 minutes, and the liquid paraffin was removed by extraction, and then dried. Furthermore, it was heat-set at 115°C to 125°C for 3 minutes to obtain a microporous film.

The stretching temperature and the heat setting temperature were appropriately adjusted for each microporous film within the specified temperature.

[Evaluation of microporous membrane]

(Evaluation of molding processability of microporous membrane)

As an evaluation index for moldability, the uniformity of the thickness of the microporous membrane was evaluated.

Specifically, for the microporous membrane obtained by the [Method for producing a microporous membrane] described above, 8 films of 100 mm × 50 mm were punched out of 250 mm × 250 mm, and Toyo Seiki Sei Co., Ltd. The film thickness was measured under the condition of 23 degreeC using the Sakusho micro thickness meter (model: KBM).

The film thickness was measured at three locations per punched film.

Then, the standard deviation of the measured values of 24 points in total was calculated, and molding processability was evaluated according to the following evaluation criteria.

(Evaluation standard)

◎ (good): less than 0.5 μm

○ (normal): 0.5 μm or more and less than 1 μm

× (defective): 1 μm or more

(Evaluation of mechanical strength of microporous membrane)

As an evaluation index of mechanical strength, the puncture strength of the microporous membrane was evaluated.

Specifically, for the microporous membrane obtained by the [Method for producing a microporous membrane] described above, 8 films of 100 mm × 50 mm were punched out of 250 mm × 250 mm, and each membrane was compressed by Kato Tech Co., Ltd. Using a testing machine (model: KES-G5), the puncture strength was measured under the conditions of a 0.5 mm radius of curvature at the tip of the needle, a piercing speed of 2 mm/s, and a temperature of 23°C. The measurement was performed at three locations per punched film.

In addition, the mass of each punched film was measured to determine the weight per unit area (film mass per 1 m2 [g]), and the punch strength in terms of weight per unit area was calculated from the following formula.

Then, the average of the measured values of 24 points was calculated as a total, and the mechanical strength was evaluated according to the following evaluation criteria.

(Punch strength in terms of weight per unit area) = (Punch strength [N])/(Weight per unit area [g/m2])

(Evaluation standard)

◎ (good): 0.85 N/(g/m 2 ) or more

○ (normal): 0.7 N/(g/m2) or more and less than 0.85 N/(g/m2)

× (poor): less than 0.7 N/(g/m 2 )

(Evaluation of dimensional stability of microporous membrane)

As an evaluation index of dimensional stability, the heat shrinkage rate of the microporous membrane was evaluated.

Specifically, for the microporous membrane obtained by the above-mentioned [Method for producing a microporous membrane], eight films of 100 mm × 50 mm were punched out of a 250 mm × 250 mm area, and left in an oven set at 120 ° C. for 60 minutes. .

After heating and cooling at room temperature for 15 minutes, the size of the microporous membrane was measured, and the thermal contraction rate (%) was calculated by the following formula.

And the average of the measured values of 8 points|pieces was calculated as a total, and dimensional stability was evaluated according to the following evaluation criteria.

(Heat shrinkage rate) = (Heat shrinkage rate in MD direction) + (Heat shrinkage rate in TD direction)

(Heat shrinkage rate in MD direction) = (1-D _MD120 /D _MD23 )×100

(Heat shrinkage rate in TD direction) = (1-D _TD120 /D _TD23 )×100

D _MD120 : Dimension in MD direction at 120°C [mm]

D _MD23 : Dimension in MD direction at 23°C [mm]

D _TD120 : TD direction dimension at 120℃ [mm]

D _TD23 : dimension in TD direction at 23°C [mm]

(Evaluation standard)

◎ (good): less than 15%

○ (normal): 15% or more and less than 25%

× (defective): 25% or more

(Evaluation of creep resistance of microporous membrane)

A sample having a width of 20 mm × a length of 100 mm was cut out from the microporous membrane obtained by the [Method of Manufacturing Microporous Membrane] described above, and the distance between chucks was 50 mm. After holding for 12 hours under conditions of a temperature of 23°C and a load of 10 N, the length of the microporous membrane was measured, and the tensile elongation (%) was calculated by the following formula.

And creep resistance was evaluated according to the following evaluation criteria.

(tensile elongation)={(L _12h /100)-1}×100

L _12h : Length of microporous membrane after 12 hours [mm]

(Evaluation standard)

◎ (good): less than 5%

○ (normal): 5% or more and less than 10%

× (defective): 10% or more

[Preparation of Ziegler-Natta catalyst]

(Preparation of Ziegler-Natta catalyst (A))

<(1) Synthesis of raw material (a-1)>

800 mL of a 2.5 mol/L hexane solution of Mg ₆ (C ₄ H ₉ ) ₁₂ AL (C ₂ H ₅ ) ₃ (corresponding to 2000 mmol of magnesium and aluminum) was charged into an 8 L stainless steel autoclave sufficiently purged with nitrogen, and While stirring at °C, 146 mL of a 5.47 mol/L n-butanolhexane solution was added dropwise over 3 hours, and the line was washed with 200 mL of hexane after completion. Furthermore, stirring was continued at 50 degreeC over 2 hours, and reaction was performed.

After completion of the reaction, what was cooled to room temperature was used as raw material (a-1). The concentration of raw material (a-1) was 1.5 mol/L of magnesium.

<(2) Synthesis of raw material (a-2)>

2,000 mL of a 1 mol/L Mg ₆ (C ₄ H ₉ ) ₁₂ AL (C ₂ H ₅ ) ₃ hexane solution (corresponding to 2000 mmol of magnesium and aluminum) was charged into an 8 L stainless steel autoclave sufficiently purged with nitrogen, and While stirring at °C, 240 mL of a hexane solution of 8.33 mol/L methylhydrodienepolysiloxane (manufactured by Shin-Etsu Chemical Industry Co., Ltd.) was pumped, and stirring was continued at 80 °C for 2 hours.

After completion of the reaction, what was cooled to normal temperature was used as raw material (a-2).

Raw material (a-2) was 0.786 mol/L in total concentration of magnesium and aluminum.

<(3) Synthesis of Carrier (a-3)>

333 mL of a 3 mol/L hexane solution of hydroxytrichlorosilane was put into an 8 L stainless steel autoclave sufficiently purged with nitrogen, and 629 mL of a hexane solution of the organic magnesium compound of the raw material (a-1) (corresponding to 943 mmol of magnesium) was added at 80 ° C. It was dripped over 3 hours, and reaction was continued stirring at 80 degreeC for 1 hour.

After completion of the reaction, the supernatant was removed and washed 4 times with 1,800 mL of hexane to obtain a carrier (a-3).

As a result of analyzing this carrier, magnesium contained per 1 g of solid was 7.5 mmol.

<(4) Preparation of Ziegler-Natta catalyst (A)>

In an 8L stainless steel autoclave sufficiently purged with nitrogen, while stirring 1,970 mL of a hexane slurry containing 110 g of the carrier (a-3) at 10 ° C., 103 mL of a 1 mol / L hexane solution of titanium tetrachloride and the above raw material ( a-2) 131 mL was added simultaneously over 3 hours.

After addition, reaction was continued at 10 degreeC for 1 hour. After completion of the reaction, the supernatant liquid was removed, and unreacted raw material components were removed by washing with hexane four times, and liquid paraffin (P-350P (trademark) manufactured by Moresco Co., Ltd.) was added as a thickener to 10 vol% (volume ratio: liquid paraffin /(liquid paraffin + hexane)) was added to prepare a Ziegler-Natta catalyst (A).

When transferring this Ziegler-Natta catalyst (A), the differential pressure between the transfer source and the transfer destination was set to 0.3 MPa.

(Preparation of Ziegler-Natta catalyst (B))

Using a 1.6 L autoclave, prepolymerization of 20 g of the Ziegler-Natta catalyst (A) described above was carried out. 800mL of normal hexane is used as a solvent, 0.4mmol of triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) is used as a cocatalyst component, and hydrogen is 20mol% (molar ratio: hydrogen/(ethylene + hydrogen)) supplied. The polymerization temperature was 20°C, and ethylene was supplied so that 5 g of polyethylene was polymerized per 1 g of the Ziegler-Natta catalyst (A). After completion of the polymerization, the supernatant was removed and washed 4 times with hexane to remove unreacted raw material components to prepare a Ziegler-Natta catalyst (B). When transferring this Ziegler-Natta catalyst (B), the differential pressure between the transfer source and the transfer destination was set to 0.8 MPa.

(Preparation of Ziegler-Natta catalyst (C))

<(5) Synthesis of Carrier (c-3)>

A carrier (c-3) was obtained in the same manner as in the synthesis of the carrier (a-3), except that the reaction temperature was 65°C. As a result of analysis of this carrier (c-3), magnesium contained per 1 g of solid was 7.5 mmol.

<(6) Preparation of Ziegler-Natta catalyst (C)>

Ziegler-Natta catalyst (C ) was prepared. When transferring this Ziegler-Natta catalyst (C), the differential pressure between the transfer source and the transfer destination was set to 0.3 MPa.

(Preparation of Ziegler-Natta catalyst (D))

<(7) Synthesis of raw material (d-1)>

_{The raw materials ( _ _ _} A raw material (d-1) was obtained by performing the same operation as in the synthesis of a-1). Raw material (d-1) was 0.7 mol/L in terms of magnesium concentration.

<(8) Synthesis of Carrier (d-3)>

The carrier (d -3) was obtained. As a result of analysis of this carrier (d-3), magnesium contained per 1 g of solid was 7.5 mmol.

<(9) Preparation of Ziegler-Natta catalyst (D)>

A Ziegler-Natta catalyst (D) was prepared by performing the same operations as in the preparation of the Ziegler-Natta catalyst (A) except that the carrier (d-3) was used instead of the carrier (a-3) and liquid paraffin was not added. was prepared. When transferring this Ziegler-Natta catalyst (D), the differential pressure between the transfer source and the transfer destination was set to 0.8 MPa.

(Preparation of Ziegler-Natta catalyst (E))

A Ziegler-Natta catalyst (E) was prepared by performing the same polymerization operation as in the preparation of the Ziegler-Natta catalyst (B), except that the Ziegler-Natta catalyst (D) was used instead of the Ziegler-Natta catalyst (A). When transferring this Ziegler-Natta catalyst (E), the differential pressure between the transfer source and the transfer destination was set to 0.3 MPa.

(Preparation of Ziegler-Natta catalyst (F))

While stirring 1600 mL of hexane at 5 ° C. in an 8 L stainless steel autoclave sufficiently purged with nitrogen, 786 mL of a 1 mol/L titanium tetrachloride hexane solution and 1000 mL of the raw material (a-2) were simultaneously added over 4 hours.

After the addition, the temperature was raised slowly and the reaction was continued at 10°C for 1 hour.

After completion of the reaction, the supernatant was removed and washed 4 times with hexane to remove unreacted raw material components to prepare a Ziegler-Natta catalyst (F).

When transferring this Ziegler-Natta catalyst (F), the differential pressure between the transfer source and the transfer destination was set to 0.8 MPa.

(Preparation of Ziegler-Natta catalyst (G))

10 vol% (volume ratio: liquid paraffin/(liquid paraffin + hexane)) of liquid paraffin (P-350P (trademark) manufactured by Moresco Co., Ltd.) was added as a thickener to the Ziegler-Natta catalyst (F), and the Ziegler-Natta catalyst (G) was prepared.

When transferring this Ziegler-Natta catalyst (G), the differential pressure between the transfer source and the transfer destination was set to 0.8 MPa.

[Production of polyethylene powder and microporous membrane]

(Example 1)

As shown below, polyethylene powder (A) is obtained by polymerizing the ethylene-based polymer (X _A ) in the polymerization reactor of the first stage and polymerizing the ethylene-based polymer (Y _A ) in the polymerization reactor of the second stage. got it

The viscosity average molecular weight of polyethylene powder (A) was 300,000, and the median diameter was 101 micrometers.

Table 1 shows the results of the various evaluations described above for the polyethylene powder (A) and the microporous membrane of the polyethylene powder (A) produced by the above-described [Method for producing a microporous membrane].

<(1) Polymerization of ethylenic polymer (X _A )>

Polymerization of the ethylenic polymer was carried out using a 300 L vessel-type polymerization reactor equipped with three swept-wing agitation blades and three baffle plates. Normal hexane was supplied as a solvent at a flow rate of 40 L/hour, the total amount was adjusted so that the slurry concentration was 16% by mass, and the stirring speed was 200 rpm. A Ziegler-Natta catalyst (A) was used as the polymerization catalyst, and it was supplied so that the production rate of the ethylenic polymer was 9.0 kg/hour. To the polymerization catalyst, STATSAFE3000 (90 g/L) diluted with normal hexane was added in an amount of 20 mass ppm relative to the production rate of the ethylene polymer. As a cocatalyst component, triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) were used and supplied at 10mmol/hour. 26 mol% of hydrogen (molar ratio: hydrogen/(ethylene+hydrogen)) was supplied. The polymerization temperature was 60°C, the polymerization pressure was 0.7 MPaG, and the average residence time was 3.3 hours.

The viscosity average molecular weight of the ethylene-based polymer (X _A ) thus obtained was 300,000. In addition, the polymerization activity in the first-stage polymerization reactor was 12,000 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was led to an intermediate flash tank at a pressure of 0.05 MPaG and a temperature of 70° C. so that the level in the polymerization reactor was kept constant, and unreacted ethylene and hydrogen were separated in the intermediate flash tank.

<(2) Polymerization of Ethylene Polymer (Y _A )>

From the intermediate flash tank described above, the polymerization slurry containing the ethylene-based polymer (X _A ) was transferred to a vessel-type 300L polymerization reactor equipped with a stirring blade of three swept blades and three baffle plates, and then the ethylene-based polymer (Y Polymerization of _A ) was performed.

The total amount was adjusted so that the slurry concentration was 40% by mass, the stirring speed was 450 rpm, and triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) were supplied as cocatalyst components at 10mmol/hour. Hydrogen was supplied at 10 mol% (molar ratio: hydrogen/(ethylene + hydrogen)). The polymerization temperature was 78°C, the polymerization pressure was 0.75 MPaG, and the average residence time was 0.75 hours so that the production rate was 11.1 kg/hour.

The viscosity average molecular weight of the ethylene-based polymer (Y _A ) thus obtained was 300,000. In addition, the polymerization activity in the second-stage polymerization reactor was 14,700 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was led to a final flash tank at a pressure of 0.05 MPaG and a temperature of 70° C. so that the level in the polymerization reactor was kept constant, and unreacted ethylene and hydrogen were separated in the final flash tank. Then, the polymerization slurry is continuously sent from the flash tank to a centrifugal separator by means of a pump, and after separating the polymer and the solvent in this centrifugal separator, the separated polyethylene powder is sent to a rotary kiln-type dryer controlled at 90° C. and blown with nitrogen After drying, polyethylene powder (A) was obtained. In addition, in this drying step, steam was sprayed on the polyethylene powder to deactivate the catalyst and cocatalyst.

(Example 2)

As shown below, polyethylene powder (B) is obtained by polymerizing the ethylene polymer (X _B ) in the polymerization reactor of the first stage and polymerizing the ethylene polymer (Y _B ) in the polymerization reactor of the second stage. got it

The viscosity average molecular weight of polyethylene powder (B) was 900,000, and the median diameter was 99 micrometers.

Table 1 shows the results of the various evaluations described above for the polyethylene powder (B) and the microporous membrane of the polyethylene powder (B) produced by the [Method for producing a microporous membrane] described above.

<(3) Polymerization of Ethylene Polymer (X _B )>

Polymerization was performed in the same manner as in (X _A ) of the above (Example 1), except that the supply amount of hydrogen was 16 mol% to obtain an ethylene-based polymer (X _B ). The viscosity average molecular weight of the obtained ethylene-based polymer (X _B ) was 900,000. In addition, the polymerization activity in the first-stage polymerization reactor was 13,000 g per 1 g of catalyst.

<(4) Polymerization of Ethylene Polymer (Y _B )>

Polymerization was performed in the same manner as in (Y _A ) in (Example 1) above, except that the stirring speed was 550 rpm and the supply amount of hydrogen was 2 mol% to obtain an ethylene-based polymer (Y _B ).

The viscosity average molecular weight of the obtained ethylene polymer (Y _B ) was 900,000. In addition, the polymerization activity in the second-stage polymerization reactor was 15,900 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was subjected to the same separation and drying operations as in the above (Example 1) to obtain polyethylene powder (B).

(Example 3)

<(5) polymerization of polyethylene powder (C)>

Polymerization of polyethylene powder was carried out using a vessel-type 300L polymerization reactor equipped with three swept-wing agitation blades and three baffle plates. Normal hexane was supplied as a solvent at a flow rate of 40 L/hour, the total amount was adjusted so that the slurry concentration was 40% by mass, and the stirring speed was 550 rpm. As a polymerization catalyst, a Ziegler-Natta catalyst (B) was used, and the polyethylene powder was supplied at a production rate of 13 kg/hour. To the polymerization catalyst, STATSAFE3000 (90 g/L) diluted with normal hexane was added in an amount of 20 mass ppm relative to the production rate of polyethylene powder. As a cocatalyst component, triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) were used and supplied at 10mmol/hour. Hydrogen was supplied in an amount of 2.9 mol% (molar ratio: hydrogen/(ethylene + hydrogen)). The polymerization temperature was 78°C, the polymerization pressure was 0.3 MPaG, and the average residence time was 3.0 hours. The polymerization slurry in the polymerization reactor was led to a flash tank at a pressure of 0.05 MPaG and a temperature of 70° C. so that the level in the polymerization reactor was kept constant, and unreacted ethylene and hydrogen were separated in the flash tank. Then, the polymerization slurry was continuously sent from the flash tank to a centrifugal separator by means of a pump, and after separating the polymer and solvent, the separated polyethylene powder was sent to a rotary kiln-type dryer controlled at 90° C. and dried while blowing with nitrogen. In addition, in this drying step, steam was sprayed on the polyethylene powder to deactivate the catalyst and cocatalyst.

Thus, the viscosity average molecular weight of the obtained polyethylene powder (C) was 900,000, and the median diameter was 110 micrometers. In addition, the polymerization activity in the polymerization reactor was 20,000 g per 1 g of catalyst.

Table 1 shows the results of the various evaluations described above for the polyethylene powder (C) and the microporous film of the polyethylene powder (C) produced by the above-described [Method for producing a microporous film].

(Example 4)

As shown below, the polyethylene powder (D) is obtained by polymerizing the ethylene polymer (X _D ) in the polymerization reactor of the first stage and polymerizing the ethylene polymer (Y _D ) in the polymerization reactor of the second stage. got it The viscosity average molecular weight of polyethylene powder (D) was 300,000, and the median diameter was 105 micrometers.

Table 1 shows the results of the various evaluations described above for the polyethylene powder (D) and the microporous membrane of the polyethylene powder (D) produced by the above-described [Method for producing a microporous membrane].

<(6) Polymerization of Ethylene Polymer (X _D )>

Except having used the Ziegler-Natta catalyst (C) as the polymerization catalyst, polymerization was performed in the same manner as in (X _A ) of the above (Example 1) to obtain an ethylene-based polymer (X _D ). The viscosity average molecular weight of the obtained ethylene polymer (X _D ) was 300,000. In addition, the polymerization activity in the first-stage polymerization reactor was 11,500 g per 1 g of catalyst.

<(7) Polymerization of Ethylene Polymer (Y _D )>

Polymerization was performed in the same manner as in (Y _A ) of the above (Example 1) to obtain an ethylene-based polymer (Y _D ). The viscosity average molecular weight of the obtained ethylene polymer (Y _D ) was 300,000. In addition, the polymerization activity in the second-stage polymerization reactor was 14,000 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was subjected to the same separation and drying operations as in the above (Example 1) to obtain polyethylene powder (D).

(Example 5)

<(8) Polymerization of polyethylene powder (E)>

Polymerization was carried out in the same manner as above (Example 3), except that the flow rate of normal hexane was 80 L / hour, the production rate was 10 kg / hour, the slurry concentration was 16 mass%, and the average residence time was 1.75 hours. ) was obtained.

Thus, the viscosity average molecular weight of the obtained polyethylene powder (E) was 900,000, and the median diameter was 108 micrometers. In addition, the polymerization activity in the polymerization reactor was 19,000 g per 1 g of catalyst.

Table 1 shows the results of the various evaluations described above for the polyethylene powder (E) and the microporous membrane of the polyethylene powder (E) produced by the above-described [Method for producing a microporous membrane].

[Example 6]

As shown below, polyethylene powder (F) is obtained by polymerizing the ethylene-based polymer (X _F ) in the polymerization reactor of the first stage and polymerizing the ethylene-based polymer (Y _F ) in the polymerization reactor of the second stage. got it

The viscosity average molecular weight of polyethylene powder (F) was 300,000, and the median diameter was 95 micrometers.

Table 1 shows the results of the various evaluations described above for the polyethylene powder (F) and the microporous membrane of the polyethylene powder (F) produced by the above-described [Method for producing a microporous membrane].

<(9) Polymerization of Ethylene Polymer (X _F )>

Polymerization was performed in the same manner as in (X _A ) of the above (Example 1) to obtain an ethylene-based polymer (X _F ). The viscosity average molecular weight of the obtained ethylene polymer (X _F ) was 300,000. In addition, the polymerization activity in the first-stage polymerization reactor was 12,000 g per 1 g of catalyst.

<(10) Polymerization of Ethylene Polymer (Y _F )>

Polymerization was performed in the same manner as in (Y _A ) in (Example 1) above, except that the slurry concentration was 30% by mass and the stirring speed was 230 rpm to obtain an ethylene-based polymer (Y _F ). The viscosity average molecular weight of the obtained ethylene polymer (Y _F ) was 300,000. In addition, the polymerization activity in the second-stage polymerization reactor was 14,500 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was separated and dried in the same manner as in the above (Example 1) to obtain polyethylene powder (F).

(Example 7)

<(11) Polymerization of polyethylene powder (G)>

Polyethylene powder (G) was obtained in the same manner as in Example 3 above, except that the production rate was 9 kg/hour, the slurry concentration was 30 mass%, and the supply amount of hydrogen was 1 mol%.

The viscosity average molecular weight of the polyethylene powder (G) thus obtained was 2,000,000, and the median diameter was 103 µm. In addition, the polymerization activity in the polymerization reactor was 18,000 g per 1 g of catalyst.

Table 1 shows the results of the various evaluations described above for the polyethylene powder (G) and the microporous membrane of the polyethylene powder (G) produced by the [Method for producing a microporous membrane] described above.

(Example 8)

As shown below, polyethylene powder (H) is obtained by polymerizing the ethylene-based polymer (X _H ) in the polymerization reactor of the first stage and polymerizing the ethylene-based polymer (Y _H ) in the polymerization reactor of the second stage. Got it. The viscosity average molecular weight of the polyethylene powder (H) was 900,000, and the median diameter was 99 µm. Table 1 shows the results of the various evaluations described above for the polyethylene powder (H) and the microporous membrane of the polyethylene powder (H) produced by the above-described [Method for producing a microporous membrane].

<(12) Polymerization of Ethylene Polymer (X _H )>

Polymerization was performed in the same manner as in (X _B ) in the above (Example 2), except that the stirring speed was 300 rpm and the slurry concentration was 30 mass% to obtain an ethylene-based polymer (X _H ). The viscosity average molecular weight of the obtained ethylene polymer (X _H ) was 900,000. In addition, the polymerization activity in the first-stage polymerization reactor was 13,000 g per 1 g of catalyst.

<(13) Polymerization of Ethylene Polymer (Y _H )>

Except having set the stirring speed to 450 rpm, polymerization was performed in the same manner as in (Y _B ) of the above (Example 2) to obtain an ethylene-based polymer (Y _H ). The viscosity average molecular weight of the obtained ethylene polymer (Y _H ) was 900,000. In addition, the polymerization activity in the second-stage polymerization reactor was 15,900 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was subjected to the same separation and drying operations as in the above (Example 1) to obtain polyethylene powder (H).

(Comparative Example 1)

<(14) Polymerization of polyethylene powder (I)>

Polyethylene powder (I) was obtained in the same manner as in the above (Example 5) except that the stirring speed was 230 rpm and the polymerization catalyst was Ziegler-Natta catalyst (E).

The viscosity average molecular weight of polyethylene powder (I) obtained in this way was 900,000, and the median diameter was 111 micrometers.

In addition, the polymerization activity in the polymerization reactor was 18,000 g per 1 g of catalyst.

Table 2 shows the results of the various evaluations described above for the polyethylene powder (I) and the microporous membrane of the polyethylene powder (I) produced by the above-described [Method for producing a microporous membrane].

(Comparative Example 2)

<(15) Polymerization of polyethylene powder (J)>

Except having used the Ziegler-Natta catalyst (D) as the polymerization catalyst, polymerization was performed in the same manner as in the above (Example 3) to obtain polyethylene powder (J).

The viscosity average molecular weight of the polyethylene powder (J) thus obtained was 900,000, and the median diameter was 113 µm. In addition, the polymerization activity in the polymerization reactor was 18,500 g per 1 g of catalyst.

Table 2 shows the results of the various evaluations described above for the polyethylene powder (J) and the microporous membrane of the polyethylene powder (J) produced by the above-described [Method for producing a microporous membrane].

(Comparative Example 3)

As shown below, polyethylene powder (K) is obtained by polymerizing the ethylene-based polymer (X _K ) in the polymerization reactor of the first stage and polymerizing the ethylene-based polymer (Y _K ) in the polymerization reactor of the second stage. Got it.

The viscosity average molecular weight of the polyethylene powder (K) was 900,000, and the median diameter was 94 µm.

Table 2 shows the results of the various evaluations described above for the polyethylene powder (K) and the microporous membrane of the polyethylene powder (K) produced by the above-described [Method for producing a microporous membrane].

<(16) Polymerization of Ethylene Polymer (X _K )>

Polymerization was performed in the same manner as in (X _B ) of the above (Example 2), except that the stirring speed was 450 rpm and the slurry concentration was 30% by mass, to obtain an ethylene-based polymer (X _K ).

The viscosity average molecular weight of the obtained ethylene-based polymer (X _K ) was 900,000. In addition, the polymerization activity in the first-stage polymerization reactor was 12,500 g per 1 g of catalyst.

<(17) Polymerization of Ethylene Polymer (Y _K )>

Polymerization was performed in the same manner as in (Y _B ) of the above (Example 2), except that the stirring speed was 230 rpm and the slurry concentration was 20% by mass, to obtain an ethylene-based polymer (Y _K ). The viscosity average molecular weight of the obtained ethylene polymer (Y _K ) was 900,000. In addition, the polymerization activity in the second-stage polymerization reactor was 15,400 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was separated and dried in the same manner as in the above (Example 1) to obtain polyethylene powder (K).

(Comparative Example 4)

<(18) Polymerization of polyethylene powder (L)>

Polyethylene powder (L) was obtained in the same manner as in Example 5 above except that the stirring speed was 230 rpm and the polymerization catalyst was Ziegler-Natta catalyst (D).

The viscosity average molecular weight of the polyethylene powder (L) thus obtained was 900,000, and the median diameter was 99 µm. In addition, the polymerization activity in the polymerization reactor was 19,000 g per 1 g of catalyst.

Table 2 shows the results of the various evaluations described above for the polyethylene powder (L) and the microporous membrane of the polyethylene powder (L) produced by the above-described [Method for producing a microporous membrane].

(Comparative Example 5)

As shown below, polyethylene powder (M) is obtained by polymerizing the ethylene-based polymer (X _M ) in the polymerization reactor of the first stage and polymerizing the ethylene-based polymer (Y _M ) in the polymerization reactor of the second stage. Got it.

The viscosity average molecular weight of the polyethylene powder (M) was 600,000, and the median diameter was 87 µm.

Table 2 shows the results of the various evaluations described above for the polyethylene powder (M) and the microporous membrane of the polyethylene powder (M) produced by the above-described [Method for producing a microporous membrane].

<(16) Polymerization of Ethylene Polymer (X _M )>

The flow rate of normal hexane was 20 L/hr, the slurry concentration was 40% by mass, the polymerization catalyst was Ziegler-Natta catalyst (F), the production rate was 13 kg/hr, the supply amount of hydrogen was 6 mol%, the polymerization temperature was 80° C., and the polymerization pressure was Except having set it as 0.5 MPaG, polymerization was performed in the same manner as in (X _B ) of the above (Example 2) to obtain an ethylene-based polymer (X _M ).

The viscosity average molecular weight of the obtained ethylene-based polymer (X _M ) was 800,000. In addition, the polymerization activity in the first-stage polymerization reactor was 70,000 g per 1 g of catalyst.

<(17) Polymerization of Ethylene Polymer (Y _M )>

Polymerization was carried out in the same manner as in (Y _B ) of (Example 2) above, except that the stirring speed was 230 rpm, the production speed was 7 kg/hour, the supply amount of hydrogen was 25 mol%, the polymerization temperature was 80° C., and the polymerization pressure was 0.5 MPaG. This was carried out to obtain an ethylene-based polymer (Y _M ). The viscosity average molecular weight of the obtained ethylene polymer (Y _M ) was 150,000. In addition, the polymerization activity in the second-stage polymerization reactor was 38,000 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was separated and dried in the same manner as in the above (Example 1) to obtain polyethylene powder (M).

(Comparative Example 6)

As shown below, polyethylene powder (N) is obtained by polymerizing the ethylene-based polymer (X _N ) in the polymerization reactor of the first stage and polymerizing the ethylene-based polymer (Y _N ) in the polymerization reactor of the second stage. Got it.

The viscosity average molecular weight of the polyethylene powder (N) was 600,000, and the median diameter was 89 µm.

Table 2 shows the results of the various evaluations described above for the polyethylene powder (N) and the microporous membrane of the polyethylene powder (N) produced by the above-described [Method for producing a microporous membrane].

<(16) Polymerization of Ethylene Polymer (X _N )>

Except for using the Ziegler-Natta catalyst (G) as the polymerization catalyst, polymerization was performed in the same manner as (X _M ) in the above (Comparative Example 5) to obtain an ethylene-based polymer (X _N ).

The viscosity average molecular weight of the obtained ethylene-based polymer (X _N ) was 800,000. In addition, the polymerization activity in the first-stage polymerization reactor was 70,000 g per 1 g of catalyst.

<(17) Polymerization of Ethylene Polymer (Y _N )>

Polymerization was performed in the same manner as in (Y _M ) of the above (Comparative Example 5) to obtain an ethylene-based polymer (Y _N ). The viscosity average molecular weight of the obtained ethylene polymer (Y _N ) was 150,000. In addition, the polymerization activity in the second-stage polymerization reactor was 38,000 g per 1 g of catalyst.

The polymerization slurry in the polymerization reactor was subjected to the same separation and drying operations as in the above (Example 1) to obtain polyethylene powder (N).

This application is based on the Japanese Patent Application (Patent Application No. 2020-196103) filed with the Japan Patent Office on November 26, 2020, the contents of which are incorporated herein by reference.

The polyethylene powder of the present invention has industrial applicability as a raw material for various shaped articles, microporous films, battery separators, and fibers.

Claims (11)

In pulse NMR, the relaxation time T of each component and the abundance ratio R of each component when 3-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method are (2) that satisfies >;
polyethylene powder.
<Requirement (1)>
At 180 ° C, the entanglement index obtained by the following (Formula I) is
12 ms or more and 25 ms or less.
(entanglement index) = T _α × R _α / (R _α + R _β ) + T _β × R _β / (R _α + R _β ) ... (Equation I)
T _α : relaxation time of the low-motile component α (ms)
R _α : presence ratio of low-motile component α (%)
T _β : relaxation time of intermediate component β (ms)
R _β : abundance of intermediate component β (%)
<Requirement (2)>
At 180 ° C, the intermediate component ratio determined by the following (Formula II) is
It is 0.25 or more and 0.5 or less.
(intermediate component ratio)=R _β /(R _α +R _β ) … (Equation II) According to claim 1, in the pulse NMR, for the abundance ratio R of the component obtained by 3-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method,
The rate of change in the abundance of the low-motile component at 180 ° C is -5% or more and 10% or less,
polyethylene powder. In pulsed NMR according to claim 1 or 2, for the component abundance ratio R obtained by 3-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method,
The rate of change in the abundance of the highly motility component at 180 ° C is 50% or less,
polyethylene powder. The method according to any one of claims 1 to 3, wherein the isothermal crystallization time at 125 ° C is 5 minutes or less,
polyethylene powder. The method according to any one of claims 1 to 4, wherein the viscosity average molecular weight is 200,000 or more and 10,000,000 or less.
polyethylene powder. The method according to any one of claims 1 to 5, wherein the median diameter is 50 μm or more and 250 μm or less,
polyethylene powder. The polyethylene powder according to any one of claims 1 to 6, which is for battery separators. A molded product of the polyethylene powder according to any one of claims 1 to 7. The molded article according to claim 8, which is a microporous film. The molded article according to claim 8, which is a fiber. The molded article according to claim 8, which is a battery separator.